Microorganisms and methods for the biosynthesis of butadiene

ABSTRACT

The invention provides non-naturally occurring microbial organisms having a butadiene pathway. The invention additionally provides methods of using such organisms to produce butadiene.

This application claims the benefit of priority of U.S. Provisionalapplication Ser. No. 61/438,947, filed Feb. 2, 2011, the entire contentsof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to biosynthetic processes, andmore specifically to organisms having butadiene biosynthetic capability.

Over 25 billion pounds of butadiene (1,3-butadiene, BD) are producedannually and is applied in the manufacture of polymers such as syntheticrubbers and ABS resins, and chemicals such as hexamethylenediamine and1,4-butanediol. Butadiene is typically produced as a by-product of thesteam cracking process for conversion of petroleum feedstocks such asnaphtha, liquefied petroleum gas, ethane or natural gas to ethylene andother olefins. The ability to manufacture butadiene from alternativeand/or renewable feedstocks would represent a major advance in the questfor more sustainable chemical production processes

One possible way to produce butadiene renewably involves fermentation ofsugars or other feedstocks to produce diols, such as 1,4-butanediol or1,3-butanediol, which are separated, purified, and then dehydrated tobutadiene in a second step involving metal-based catalysis. Directfermentative production of butadiene from renewable feedstocks wouldobviate the need for dehydration steps and butadiene gas (bp −4.4° C.)would be continuously emitted from the fermenter and readily condensedand collected. Developing a fermentative production process wouldeliminate the need for fossil-based butadiene and would allowsubstantial savings in cost, energy, and harmful waste and emissionsrelative to petrochemically-derived butadiene.

Microbial organisms and methods for effectively producing butadiene fromcheap renewable feedstocks such as molasses, sugar cane juice, andsugars derived from biomass sources, including agricultural and woodwaste, as well as C1 feedstocks such as syngas and carbon dioxide, aredescribed herein and include related advantages.

SUMMARY OF THE INVENTION

The invention provides non-naturally occurring microbial organismscontaining butadiene pathways comprising at least one exogenous nucleicacid encoding a butadiene pathway enzyme expressed in a sufficientamount to produce butadiene. The invention additionally provides methodsof using such microbial organisms to produce butadiene, by culturing anon-naturally occurring microbial organism containing butadiene pathwaysas described herein under conditions and for a sufficient period of timeto produce butadiene.

In some aspects, embodiments disclosed herein relate to a process forthe production of butadiene that includes (a) culturing by fermentationin a sufficient amount of nutrients and media a non-naturally occurringmicrobial organism that produces crotyl alcohol; and (b) convertingcrotyl alcohol, produced by culturing the non-naturally occurringmicrobial organism, to butadiene.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a natural pathway to isoprenoids and terpenes. Enzymes fortransformation of the identified substrates to products include: A.acetyl-CoA:acetyl-CoA acyltransferase, B. hydroxymethylglutaryl-CoAsynthase, C. 3-hydroxy-3-methylglutaryl-CoA reductase (alcohol forming),D. mevalonate kinase, E. phosphomevalonate kinase, F.diphosphomevalonate decarboxylase, G. isopentenyl-diphosphate isomerase,H. isoprene synthase.

FIG. 2 shows exemplary pathways for production of butadiene fromacetyl-CoA, glutaconyl-CoA, glutaryl-CoA, 3-aminobutyryl-CoA or4-hydroxybutyryl-CoA via crotyl alcohol. Enzymes for transformation ofthe identified substrates to products include: A. acetyl-CoA:acetyl-CoAacyltransferase, B. acetoacetyl-CoA reductase, C. 3-hydroxybutyryl-CoAdehydratase, D. crotonyl-CoA reductase (aldehyde forming), E.crotonaldehyde reductase (alcohol forming), F. crotyl alcohol kinase, G.2-butenyl-4-phosphate kinase, H. butadiene synthase, I. crotonyl-CoAhydrolase, synthetase, transferase, J. crotonate reductase, K.crotonyl-CoA reductase (alcohol forming), L. glutaconyl-CoAdecarboxylase, M., glutaryl-CoA dehydrogenase, N. 3-aminobutyryl-CoAdeaminase, O. 4-hydroxybutyryl-CoA dehydratase, P. crotyl alcoholdiphosphokinase. The chemical pathway to butadiene utilizes dehydrationprocesses.

FIG. 3 shows exemplary pathways for production of butadiene fromerythrose-4-phosphate. Enzymes for transformation of the identifiedsubstrates to products include: A. Erythrose-4-phosphate reductase, B.Erythritol-4-phospate cytidylyltransferase, C. 4-(cytidine5′-diphospho)-erythritol kinase, D. Erythritol 2,4-cyclodiphosphatesynthase, E. 1-Hydroxy-2-butenyl 4-diphosphate synthase, F.1-Hydroxy-2-butenyl 4-diphosphate reductase, G. Butenyl 4-diphosphateisomerase, H. Butadiene synthase I. Erythrose-4-phosphate kinase, J.Erythrose reductase, K. Erythritol kinase.

FIG. 4 shows an exemplary pathway for production of butadiene frommalonyl-CoA plus acetyl-CoA. Enzymes for transformation of theidentified substrates to products include: A. malonyl-CoA:acetyl-CoAacyltransferase, B. 3-oxoglutaryl-CoA reductase (ketone-reducing), C.3-hydroxyglutaryl-CoA reductase (aldehyde forming), D.3-hydroxy-5-oxopentanoate reductase, E. 3,5-dihydroxypentanoate kinase,F. 3H5PP kinase, G. 3H5PDP decarboxylase, H. butenyl 4-diphosphateisomerase, I. butadiene synthase, J. 3-hydroxyglutaryl-CoA reductase(alcohol forming), K. 3-oxoglutaryl-CoA reductase (aldehyde forming), L.3,5-dioxopentanoate reductase (ketone reducing), M. 3,5-dioxopentanoatereductase (aldehyde reducing), N. 5-hydroxy-3-oxopentanoate reductase,O. 3-oxo-glutaryl-CoA reductase (CoA reducing and alcohol forming).Compound abbreviations include:3H5PP=3-Hydroxy-5-phosphonatooxypentanoate and3H5PDP=3-Hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoate.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to the design and production of cellsand organisms having biosynthetic production capabilities for butadiene.The invention, in particular, relates to the design of microbialorganism capable of producing butadiene by introducing one or morenucleic acids encoding a butadiene pathway enzyme.

In one embodiment, the invention utilizes in silico stoichiometricmodels of Escherichia coli metabolism that identify metabolic designsfor biosynthetic production of butadiene. The results described hereinindicate that metabolic pathways can be designed and recombinantlyengineered to achieve the biosynthesis of butadiene in Escherichia coliand other cells or organisms. Biosynthetic production of butadiene, forexample, for the in silico designs can be confirmed by construction ofstrains having the designed metabolic genotype. These metabolicallyengineered cells or organisms also can be subjected to adaptiveevolution to further augment butadiene biosynthesis, including underconditions approaching theoretical maximum growth.

In certain embodiments, the butadiene biosynthesis characteristics ofthe designed strains make them genetically stable and particularlyuseful in continuous bioprocesses. Separate strain design strategieswere identified with incorporation of different non-native orheterologous reaction capabilities into E. coli or other host organismsleading to butadiene producing metabolic pathways from acetyl-CoA,glutaconyl-CoA, glutaryl-CoA, 3-aminobutyryl-CoA, 4-hydroxybutyryl-CoA,erythrose-4-phosphate or malonyl-CoA plus acetyl-CoA. In silicometabolic designs were identified that resulted in the biosynthesis ofbutadiene in microorganisms from each of these substrates or metabolicintermediates.

Strains identified via the computational component of the platform canbe put into actual production by genetically engineering any of thepredicted metabolic alterations, which lead to the biosyntheticproduction of butadiene or other intermediate and/or downstreamproducts. In yet a further embodiment, strains exhibiting biosyntheticproduction of these compounds can be further subjected to adaptiveevolution to further augment product biosynthesis. The levels of productbiosynthesis yield following adaptive evolution also can be predicted bythe computational component of the system.

The maximum theoretical butadiene yield from glucose is 1.09 mol/mol(0.33 g/g).

11C₆H₁₂O₆=12C₄H₆+18CO₂+30H₂O

The pathways presented in FIGS. 2 and 4 achieve a yield of 1.0 molesbutadiene per mole of glucose utilized. Increasing product yields totheoretical maximum value is possible if cells are capable of fixing CO₂through pathways such as the reductive (or reverse) TCA cycle or theWood-Ljungdahl pathway. Organisms engineered to possess the pathwaydepicted in FIG. 3 are also capable of reaching near theoretical maximumyields of butadiene.

As used herein, the term “non-naturally occurring” when used inreference to a microbial organism or microorganism of the invention isintended to mean that the microbial organism has at least one geneticalteration not normally found in a naturally occurring strain of thereferenced species, including wild-type strains of the referencedspecies. Genetic alterations include, for example, modificationsintroducing expressible nucleic acids encoding metabolic polypeptides,other nucleic acid additions, nucleic acid deletions and/or otherfunctional disruption of the microbial organism's genetic material. Suchmodifications include, for example, coding regions and functionalfragments thereof, for heterologous, homologous or both heterologous andhomologous polypeptides for the referenced species. Additionalmodifications include, for example, non-coding regulatory regions inwhich the modifications alter expression of a gene or operon. Exemplarymetabolic polypeptides include enzymes or proteins within a butadienebiosynthetic pathway.

A metabolic modification refers to a biochemical reaction that isaltered from its naturally occurring state. Therefore, non-naturallyoccurring microorganisms can have genetic modifications to nucleic acidsencoding metabolic polypeptides, or functional fragments thereof.Exemplary metabolic modifications are disclosed herein.

As used herein, the term “butadiene,” having the molecular formula C₄H₆and a molecular mass of 54.09 g/mol (see FIGS. 2-4) (IUPAC nameButa-1,3-diene) is used interchangeably throughout with 1,3-butadiene,biethylene, erythrene, divinyl, vinylethylene. Butadiene is a colorless,non corrosive liquefied gas with a mild aromatic or gasoline-like odor.Butadiene is both explosive and flammable because of its low flashpoint.

As used herein, the term “isolated” when used in reference to amicrobial organism is intended to mean an organism that is substantiallyfree of at least one component as the referenced microbial organism isfound in nature. The term includes a microbial organism that is removedfrom some or all components as it is found in its natural environment.The term also includes a microbial organism that is removed from some orall components as the microbial organism is found in non-naturallyoccurring environments. Therefore, an isolated microbial organism ispartly or completely separated from other substances as it is found innature or as it is grown, stored or subsisted in non-naturally occurringenvironments. Specific examples of isolated microbial organisms includepartially pure microbes, substantially pure microbes and microbescultured in a medium that is non-naturally occurring.

As used herein, the terms “microbial,” “microbial organism” or“microorganism” are intended to mean any organism that exists as amicroscopic cell that is included within the domains of archaea,bacteria or eukarya. Therefore, the term is intended to encompassprokaryotic or eukaryotic cells or organisms having a microscopic sizeand includes bacteria, archaea and eubacteria of all species as well aseukaryotic microorganisms such as yeast and fungi. The term alsoincludes cell cultures of any species that can be cultured for theproduction of a biochemical.

As used herein, the term “CoA” or “coenzyme A” is intended to mean anorganic cofactor or prosthetic group (nonprotein portion of an enzyme)whose presence is required for the activity of many enzymes (theapoenzyme) to form an active enzyme system. Coenzyme A functions incertain condensing enzymes, acts in acetyl or other acyl group transferand in fatty acid synthesis and oxidation, pyruvate oxidation and inother acetylation.

As used herein, the term “substantially anaerobic” when used inreference to a culture or growth condition is intended to mean that theamount of oxygen is less than about 10% of saturation for dissolvedoxygen in liquid media. The term also is intended to include sealedchambers of liquid or solid medium maintained with an atmosphere of lessthan about 1% oxygen.

“Exogenous” as it is used herein is intended to mean that the referencedmolecule or the referenced activity is introduced into the hostmicrobial organism. The molecule can be introduced, for example, byintroduction of an encoding nucleic acid into the host genetic materialsuch as by integration into a host chromosome or as non-chromosomalgenetic material such as a plasmid. Therefore, the term as it is used inreference to expression of an encoding nucleic acid refers tointroduction of the encoding nucleic acid in an expressible form intothe microbial organism. When used in reference to a biosyntheticactivity, the term refers to an activity that is introduced into thehost reference organism. The source can be, for example, a homologous orheterologous encoding nucleic acid that expresses the referencedactivity following introduction into the host microbial organism.Therefore, the term “endogenous” refers to a referenced molecule oractivity that is present in the host. Similarly, the term when used inreference to expression of an encoding nucleic acid refers to expressionof an encoding nucleic acid contained within the microbial organism. Theterm “heterologous” refers to a molecule or activity derived from asource other than the referenced species whereas “homologous” refers toa molecule or activity derived from the host microbial organism.Accordingly, exogenous expression of an encoding nucleic acid of theinvention can utilize either or both a heterologous or homologousencoding nucleic acid.

It is understood that when more than one exogenous nucleic acid isincluded in a microbial organism that the more than one exogenousnucleic acids refers to the referenced encoding nucleic acid orbiosynthetic activity, as discussed above. It is further understood, asdisclosed herein, that such more than one exogenous nucleic acids can beintroduced into the host microbial organism on separate nucleic acidmolecules, on polycistronic nucleic acid molecules, or a combinationthereof, and still be considered as more than one exogenous nucleicacid. For example, as disclosed herein a microbial organism can beengineered to express two or more exogenous nucleic acids encoding adesired pathway enzyme or protein. In the case where two exogenousnucleic acids encoding a desired activity are introduced into a hostmicrobial organism, it is understood that the two exogenous nucleicacids can be introduced as a single nucleic acid, for example, on asingle plasmid, on separate plasmids, can be integrated into the hostchromosome at a single site or multiple sites, and still be consideredas two exogenous nucleic acids. Similarly, it is understood that morethan two exogenous nucleic acids can be introduced into a host organismin any desired combination, for example, on a single plasmid, onseparate plasmids, can be integrated into the host chromosome at asingle site or multiple sites, and still be considered as two or moreexogenous nucleic acids, for example three exogenous nucleic acids.Thus, the number of referenced exogenous nucleic acids or biosyntheticactivities refers to the number of encoding nucleic acids or the numberof biosynthetic activities, not the number of separate nucleic acidsintroduced into the host organism.

The non-naturally occurring microbial organisms of the invention cancontain stable genetic alterations, which refers to microorganisms thatcan be cultured for greater than five generations without loss of thealteration. Generally, stable genetic alterations include modificationsthat persist greater than 10 generations, particularly stablemodifications will persist more than about 25 generations, and moreparticularly, stable genetic modifications will be greater than 50generations, including indefinitely.

Those skilled in the art will understand that the genetic alterations,including metabolic modifications exemplified herein, are described withreference to a suitable host organism such as E. coli and theircorresponding metabolic reactions or a suitable source organism fordesired genetic material such as genes for a desired metabolic pathway.However, given the complete genome sequencing of a wide variety oforganisms and the high level of skill in the area of genomics, thoseskilled in the art will readily be able to apply the teachings andguidance provided herein to essentially all other organisms. Forexample, the E. coli metabolic alterations exemplified herein canreadily be applied to other species by incorporating the same oranalogous encoding nucleic acid from species other than the referencedspecies. Such genetic alterations include, for example, geneticalterations of species homologs, in general, and in particular,orthologs, paralogs or nonorthologous gene displacements.

An ortholog is a gene or genes that are related by vertical descent andare responsible for substantially the same or identical functions indifferent organisms. For example, mouse epoxide hydrolase and humanepoxide hydrolase can be considered orthologs for the biologicalfunction of hydrolysis of epoxides. Genes are related by verticaldescent when, for example, they share sequence similarity of sufficientamount to indicate they are homologous, or related by evolution from acommon ancestor. Genes can also be considered orthologs if they sharethree-dimensional structure but not necessarily sequence similarity, ofa sufficient amount to indicate that they have evolved from a commonancestor to the extent that the primary sequence similarity is notidentifiable. Genes that are orthologous can encode proteins withsequence similarity of about 25% to 100% amino acid sequence identity.Genes encoding proteins sharing an amino acid similarity less that 25%can also be considered to have arisen by vertical descent if theirthree-dimensional structure also shows similarities. Members of theserine protease family of enzymes, including tissue plasminogenactivator and elastase, are considered to have arisen by verticaldescent from a common ancestor.

Orthologs include genes or their encoded gene products that through, forexample, evolution, have diverged in structure or overall activity. Forexample, where one species encodes a gene product exhibiting twofunctions and where such functions have been separated into distinctgenes in a second species, the three genes and their correspondingproducts are considered to be orthologs. For the production of abiochemical product, those skilled in the art will understand that theorthologous gene harboring the metabolic activity to be introduced ordisrupted is to be chosen for construction of the non-naturallyoccurring microorganism. An example of orthologs exhibiting separableactivities is where distinct activities have been separated intodistinct gene products between two or more species or within a singlespecies. A specific example is the separation of elastase proteolysisand plasminogen proteolysis, two types of serine protease activity, intodistinct molecules as plasminogen activator and elastase. A secondexample is the separation of mycoplasma 5′-3′ exonuclease and DrosophilaDNA polymerase III activity. The DNA polymerase from the first speciescan be considered an ortholog to either or both of the exonuclease orthe polymerase from the second species and vice versa.

In contrast, paralogs are homologs related by, for example, duplicationfollowed by evolutionary divergence and have similar or common, but notidentical functions. Paralogs can originate or derive from, for example,the same species or from a different species. For example, microsomalepoxide hydrolase (epoxide hydrolase I) and soluble epoxide hydrolase(epoxide hydrolase II) can be considered paralogs because they representtwo distinct enzymes, co-evolved from a common ancestor, that catalyzedistinct reactions and have distinct functions in the same species.Paralogs are proteins from the same species with significant sequencesimilarity to each other suggesting that they are homologous, or relatedthrough co-evolution from a common ancestor. Groups of paralogousprotein families include HipA homologs, luciferase genes, peptidases,and others.

A nonorthologous gene displacement is a nonorthologous gene from onespecies that can substitute for a referenced gene function in adifferent species. Substitution includes, for example, being able toperform substantially the same or a similar function in the species oforigin compared to the referenced function in the different species.Although generally, a nonorthologous gene displacement will beidentifiable as structurally related to a known gene encoding thereferenced function, less structurally related but functionally similargenes and their corresponding gene products nevertheless will still fallwithin the meaning of the term as it is used herein. Functionalsimilarity requires, for example, at least some structural similarity inthe active site or binding region of a nonorthologous gene productcompared to a gene encoding the function sought to be substituted.Therefore, a nonorthologous gene includes, for example, a paralog or anunrelated gene.

Therefore, in identifying and constructing the non-naturally occurringmicrobial organisms of the invention having butadiene biosyntheticcapability, those skilled in the art will understand with applying theteaching and guidance provided herein to a particular species that theidentification of metabolic modifications can include identification andinclusion or inactivation of orthologs. To the extent that paralogsand/or nonorthologous gene displacements are present in the referencedmicroorganism that encode an enzyme catalyzing a similar orsubstantially similar metabolic reaction, those skilled in the art alsocan utilize these evolutionally related genes.

Orthologs, paralogs and nonorthologous gene displacements can bedetermined by methods well known to those skilled in the art. Forexample, inspection of nucleic acid or amino acid sequences for twopolypeptides will reveal sequence identity and similarities between thecompared sequences. Based on such similarities, one skilled in the artcan determine if the similarity is sufficiently high to indicate theproteins are related through evolution from a common ancestor.Algorithms well known to those skilled in the art, such as Align, BLAST,Clustal W and others compare and determine a raw sequence similarity oridentity, and also determine the presence or significance of gaps in thesequence which can be assigned a weight or score. Such algorithms alsoare known in the art and are similarly applicable for determiningnucleotide sequence similarity or identity. Parameters for sufficientsimilarity to determine relatedness are computed based on well knownmethods for calculating statistical similarity, or the chance of findinga similar match in a random polypeptide, and the significance of thematch determined. A computer comparison of two or more sequences can, ifdesired, also be optimized visually by those skilled in the art. Relatedgene products or proteins can be expected to have a high similarity, forexample, 25% to 100% sequence identity. Proteins that are unrelated canhave an identity which is essentially the same as would be expected tooccur by chance, if a database of sufficient size is scanned (about 5%).Sequences between 5% and 24% may or may not represent sufficienthomology to conclude that the compared sequences are related. Additionalstatistical analysis to determine the significance of such matches giventhe size of the data set can be carried out to determine the relevanceof these sequences.

Exemplary parameters for determining relatedness of two or moresequences using the BLAST algorithm, for example, can be as set forthbelow. Briefly, amino acid sequence alignments can be performed usingBLASTP version 2.0.8 (Jan. 5, 1999) and the following parameters:Matrix: 0 BLOSUM62; gap open: 11; gap extension: 1; x_dropoff: 50;expect: 10.0; wordsize: 3; filter: on. Nucleic acid sequence alignmentscan be performed using BLASTN version 2.0.6 (Sep. 16, 1998) and thefollowing parameters: Match: 1; mismatch: −2; gap open: 5; gapextension: 2; x_dropoff: 50; expect: 10.0; wordsize: 11; filter: off.Those skilled in the art will know what modifications can be made to theabove parameters to either increase or decrease the stringency of thecomparison, for example, and determine the relatedness of two or moresequences.

In some embodiments, the invention provides a non-naturally occurringmicrobial organism, including a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding a butadienepathway enzyme expressed in a sufficient amount to produce butadiene,the butadiene pathway including an acetyl-CoA:acetyl-CoAacyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoAdehydratase, a crotonyl-CoA reductase (aldehyde forming), acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase, a crotonyl-CoAhydrolase, synthetase, or transferase, a crotonate reductase, acrotonyl-CoA reductase (alcohol forming), a glutaconyl-CoAdecarboxylase, a glutaryl-CoA dehydrogenase, a 3-aminobutyryl-CoAdeaminase, a 4-hydroxybutyryl-CoA dehydratase or a crotyl alcoholdiphosphokinase (FIG. 2). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including an acetyl-CoA:acetyl-CoAacyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoAdehydratase, a crotonyl-CoA reductase (aldehyde forming), acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase and a butadiene synthase (FIG. 2, stepsA-H). In one aspect, the non-naturally occurring microbial organismincludes a microbial organism having a butadiene pathway having at leastone exogenous nucleic acid encoding butadiene pathway enzymes expressedin a sufficient amount to produce butadiene, the butadiene pathwayincluding an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoAreductase, a 3-hydroxybutyryl-CoA dehydratase, a crotyl alcohol kinase,a 2-butenyl-4-phosphate kinase, a butadiene synthase and crotonyl-CoAreductase (alcohol forming) (FIG. 2, steps A-C, K, F, G, H). In oneaspect, the non-naturally occurring microbial organism includes amicrobial organism having a butadiene pathway having at least oneexogenous nucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includingan acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase,a 3-hydroxybutyryl-CoA dehydratase, a butadiene synthase, a crotonyl-CoAreductase (alcohol forming) and a crotyl alcohol diphosphokinase (FIG.2, steps A-C, K, P, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including an acetyl-CoA:acetyl-CoAacyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoAdehydratase, a crotonaldehyde reductase (alcohol forming), a crotylalcohol kinase, a 2-butenyl-4-phosphate kinase, a butadiene synthase, acrotonyl-CoA hydrolase, synthetase, or transferase and a crotonatereductase, (FIG. 2, steps A-C, I, J, E, F, G, H). In one aspect, thenon-naturally occurring microbial organism includes a microbial organismhaving a butadiene pathway having at least one exogenous nucleic acidencoding butadiene pathway enzymes expressed in a sufficient amount toproduce butadiene, the butadiene pathway including anacetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a3-hydroxybutyryl-CoA dehydratase, a crotonaldehyde reductase (alcoholforming), a butadiene synthase, a crotonyl-CoA hydrolase, synthetase ortransferase, a crotonate reductase and a crotyl alcohol diphosphokinase(FIG. 2, steps A-C, I, J, E, P, H). In one aspect, the non-naturallyoccurring microbial organism includes a microbial organism having abutadiene pathway having at least one exogenous nucleic acid encodingbutadiene pathway enzymes expressed in a sufficient amount to producebutadiene, the butadiene pathway including an acetyl-CoA:acetyl-CoAacyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoAdehydratase, a crotonyl-CoA reductase (aldehyde forming), acrotonaldehyde reductase (alcohol forming), a butadiene synthase and acrotyl alcohol diphosphokinase (FIG. 2, steps A-E, P, H). In one aspect,the non-naturally occurring microbial organism includes a microbialorganism having a butadiene pathway having at least one exogenousnucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga glutaconyl-CoA decarboxylase, a crotonyl-CoA reductase (aldehydeforming), a crotonaldehyde reductase (alcohol forming), a crotyl alcoholkinase, a 2-butenyl-4-phosphate kinase and a butadiene synthase (FIG. 2,steps L, D-H). In one aspect, the non-naturally occurring microbialorganism includes a microbial organism having a butadiene pathway havingat least one exogenous nucleic acid encoding butadiene pathway enzymesexpressed in a sufficient amount to produce butadiene, the butadienepathway including a glutaconyl-CoA decarboxylase, a crotyl alcoholkinase, a 2-butenyl-4-phosphate kinase, a butadiene synthase andcrotonyl-CoA reductase (alcohol forming) (FIG. 2, steps L, K, F, G, H).In one aspect, the non-naturally occurring microbial organism includes amicrobial organism having a butadiene pathway having at least oneexogenous nucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga glutaconyl-CoA decarboxylase, a butadiene synthase, a crotonyl-CoAreductase (alcohol forming) and a crotyl alcohol diphosphokinase (FIG.2, steps L, K, P, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a glutaconyl-CoA decarboxylase, acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase, a crotonyl-CoAhydrolase, synthetase, or transferase and a crotonate reductase (FIG. 2,steps L, I, J, E, F, G, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a glutaconyl-CoA decarboxylase, acrotonaldehyde reductase (alcohol forming), a butadiene synthase, acrotonyl-CoA hydrolase, synthetase or transferase, a crotonate reductaseand a crotyl alcohol diphosphokinase (FIG. 2, steps L, I, J, E, P, H).In one aspect, the non-naturally occurring microbial organism includes amicrobial organism having a butadiene pathway having at least oneexogenous nucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehydeforming), a crotonaldehyde reductase (alcohol forming), a butadiene aglutaconyl-CoA decarboxylase and a crotyl alcohol diphosphokinase (FIG.2, steps L, C, D, E, P, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a glutaryl-CoA dehydrogenase, acrotonyl-CoA reductase (aldehyde forming), a crotonaldehyde reductase(alcohol forming), a crotyl alcohol kinase, a 2-butenyl-4-phosphatekinase and a butadiene synthase (FIG. 2, steps M, D-H). In one aspect,the non-naturally occurring microbial organism includes a microbialorganism having a butadiene pathway having at least one exogenousnucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga glutaryl-CoA dehydrogenase, a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase and crotonyl-CoAreductase (alcohol forming) (FIG. 2, steps M, K, F, G, H). In oneaspect, the non-naturally occurring microbial organism includes amicrobial organism having a butadiene pathway having at least oneexogenous nucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga glutaryl-CoA dehydrogenase, a butadiene synthase, a crotonyl-CoAreductase (alcohol forming) and a crotyl alcohol diphosphokinase (FIG.2, steps M, K, P, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a glutaryl-CoA dehydrogenase, acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase, a crotonyl-CoAhydrolase, synthetase, or transferase and a crotonate reductase (FIG. 2,steps M, I, J, E, F, G, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a glutaryl-CoA dehydrogenase, acrotonaldehyde reductase (alcohol forming), a butadiene synthase, acrotonyl-CoA hydrolase, synthetase or transferase, a crotonate reductaseand a crotyl alcohol diphosphokinase (FIG. 2, steps M, I, J, E, P, H).In one aspect, the non-naturally occurring microbial organism includes amicrobial organism having a butadiene pathway having at least oneexogenous nucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehydeforming), a crotonaldehyde reductase (alcohol forming), a butadienesynthase, a glutaryl-CoA dehydrogenase and a crotyl alcoholdiphosphokinase (FIG. 2, steps M, C, D, E, P, H). In one aspect, thenon-naturally occurring microbial organism includes a microbial organismhaving a butadiene pathway having at least one exogenous nucleic acidencoding butadiene pathway enzymes expressed in a sufficient amount toproduce butadiene, the butadiene pathway including a 3-aminobutyryl-CoAdeaminase, a crotonyl-CoA reductase (aldehyde forming), a crotonaldehydereductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase and a butadiene synthase (FIG. 2, steps N,D-H). In one aspect, the non-naturally occurring microbial organismincludes a microbial organism having a butadiene pathway having at leastone exogenous nucleic acid encoding butadiene pathway enzymes expressedin a sufficient amount to produce butadiene, the butadiene pathwayincluding a 3-aminobutyryl-CoA deaminase, a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase and crotonyl-CoAreductase (alcohol forming) (FIG. 2, steps N, K, F, G, H). In oneaspect, the non-naturally occurring microbial organism includes amicrobial organism having a butadiene pathway having at least oneexogenous nucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga 3-aminobutyryl-CoA deaminase, a butadiene synthase, a crotonyl-CoAreductase (alcohol forming) and a crotyl alcohol diphosphokinase (FIG.2, steps N, K, P, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a 3-aminobutyryl-CoA deaminase, acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase, a crotonyl-CoAhydrolase, synthetase, or transferase and a crotonate reductase (FIG. 2,steps N, I, J, E, F, G, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a 3-aminobutyryl-CoA deaminase, acrotonaldehyde reductase (alcohol forming), a butadiene synthase, acrotonyl-CoA hydrolase, synthetase or transferase, a crotonate reductaseand a crotyl alcohol diphosphokinase (FIG. 2, steps N, I, J, E, P, H).In one aspect, the non-naturally occurring microbial organism includes amicrobial organism having a butadiene pathway having at least oneexogenous nucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehydeforming), a crotonaldehyde reductase (alcohol forming), a butadienesynthase, a 3-aminobutyryl-CoA deaminase and a crotyl alcoholdiphosphokinase (FIG. 2, steps N, C, D, E, P, H). In one aspect, thenon-naturally occurring microbial organism includes a microbial organismhaving a butadiene pathway having at least one exogenous nucleic acidencoding butadiene pathway enzymes expressed in a sufficient amount toproduce butadiene, the butadiene pathway including a4-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehydeforming), a crotonaldehyde reductase (alcohol forming), a crotyl alcoholkinase, a 2-butenyl-4-phosphate kinase and a butadiene synthase (FIG. 2,steps O, D-H). In one aspect, the non-naturally occurring microbialorganism includes a microbial organism having a butadiene pathway havingat least one exogenous nucleic acid encoding butadiene pathway enzymesexpressed in a sufficient amount to produce butadiene, the butadienepathway including a 4-hydroxybutyryl-CoA dehydratase, a crotyl alcoholkinase, a 2-butenyl-4-phosphate kinase, a butadiene synthase andcrotonyl-CoA reductase (alcohol forming) (FIG. 2, steps O, K, F, G, H).In one aspect, the non-naturally occurring microbial organism includes amicrobial organism having a butadiene pathway having at least oneexogenous nucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga 4-hydroxybutyryl-CoA dehydratase, a butadiene synthase, a crotonyl-CoAreductase (alcohol forming) and a crotyl alcohol diphosphokinase (FIG.2, steps O, K, P, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a 4-hydroxybutyryl-CoA dehydratase, acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase, a crotonyl-CoAhydrolase, synthetase, or transferase and a crotonate reductase (FIG. 2,steps O, I, J, E, F, G, H). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a 4-hydroxybutyryl-CoA dehydratase, acrotonaldehyde reductase (alcohol forming), a butadiene synthase, acrotonyl-CoA hydrolase, synthetase or transferase, a crotonate reductaseand a crotyl alcohol diphosphokinase (FIG. 2, steps O, I, J, E, P, H).In one aspect, the non-naturally occurring microbial organism includes amicrobial organism having a butadiene pathway having at least oneexogenous nucleic acid encoding butadiene pathway enzymes expressed in asufficient amount to produce butadiene, the butadiene pathway includinga 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehydeforming), a crotonaldehyde reductase (alcohol forming), a butadienesynthase, a 4-hydroxybutyryl-CoA dehydratase and a crotyl alcoholdiphosphokinase (FIG. 2, steps L, C, D, E, P, H).

In some embodiments, the invention provides a non-naturally occurringmicrobial organism comprising a crotyl alcohol pathway. The crotylalcohol pathway includes at least one exogenous nucleic acid encoding acrotyl alcohol pathway enzyme expressed in a sufficient amount toproduce crotyl alcohol. The crotyl alcohol pathway includes anacetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehydeforming), a crotonaldehyde reductase (alcohol forming), a crotonyl-CoAhydrolase, synthetase, or transferase, a crotonate reductase, acrotonyl-CoA reductase (alcohol forming), a glutaconyl-CoAdecarboxylase, a glutaryl-CoA dehydrogenase, a 3-aminobutyryl-CoAdeaminase, or a 4-hydroxybutyryl-CoA dehydratase.

In some embodiments, the microbial organism comprises two exogenousnucleic acids each encoding a crotyl alcohol pathway enzyme, in otherembodiments, the microbial organism includes three exogenous nucleicacids each encoding a crotyl alcohol pathway enzyme, in still furtherembodiments the microbial organism includes four exogenous nucleic acidseach encoding a crotyl alcohol pathway enzyme.

In some embodiments, the crotyl alcohol pathway includes anacetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehydeforming), and a crotonaldehyde reductase (alcohol forming). In someembodiments, the crotyl alcohol pathway includes anacetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a3-hydroxybutyryl-CoA dehydratase, and a crotonyl-CoA reductase (alcoholforming). In some embodiments, the crotyl alcohol pathway includes anacetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a3-hydroxybutyryl-CoA dehydratase, a crotonaldehyde reductase (alcoholforming), a crotonyl-CoA hydrolase, synthetase or transferase and acrotonate reductase. In some embodiments, the crotyl alcohol pathwayincludes a glutaconyl-CoA decarboxylase, a crotonyl-CoA reductase(aldehyde forming), and a crotonaldehyde reductase (alcohol forming). Insome embodiments, the crotyl alcohol pathway includes a glutaconyl-CoAdecarboxylase and crotonyl-CoA reductase (alcohol forming). In someembodiments, the crotyl alcohol pathway includes a glutaconyl-CoAdecarboxylase, a crotonaldehyde reductase (alcohol forming), acrotonyl-CoA hydrolase, synthetase, or transferase and a crotonatereductase. In some embodiments, the crotyl alcohol pathway includes aglutaryl-CoA dehydrogenase, a crotonyl-CoA reductase (aldehyde forming),and a crotonaldehyde reductase (alcohol forming). In some embodiments,the crotyl alcohol pathway includes a glutaryl-CoA dehydrogenase andcrotonyl-CoA reductase (alcohol forming). In some embodiments, thecrotyl alcohol pathway includes a glutaryl-CoA dehydrogenase, acrotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase,synthetase, or transferase and a crotonate reductase. In someembodiments, the crotyl alcohol pathway includes a 3-aminobutyryl-CoAdeaminase, a crotonyl-CoA reductase (aldehyde forming), and acrotonaldehyde reductase (alcohol forming). In some embodiments, thecrotyl alcohol pathway includes a 3-aminobutyryl-CoA deaminase andcrotonyl-CoA reductase (alcohol forming). In some embodiments, thecrotyl alcohol pathway includes a 3-aminobutyryl-CoA deaminase, acrotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase,synthetase or transferase and a crotonate reductase. In someembodiments, the crotyl alcohol pathway includes a 4-hydroxybutyryl-CoAdehydratase, a crotonyl-CoA reductase (aldehyde forming), and acrotonaldehyde reductase (alcohol forming). In some embodiments, thecrotyl alcohol pathway includes a 4-hydroxybutyryl-CoA dehydratase andcrotonyl-CoA reductase (alcohol forming). In some embodiments, thecrotyl alcohol pathway includes a 4-hydroxybutyryl-CoA dehydratase, acrotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase,synthetase or transferase and a crotonate reductase. In someembodiments, the non-naturally occurring microbial organism having acrotyl alcohol pathway has at least one exogenous nucleic acid that is aheterologous nucleic acid. In some embodiments, the non-naturallyoccurring microbial organism having a crotyl alcohol pathway is in asubstantially anaerobic culture medium.

In some embodiments, the invention provides a non-naturally occurringmicrobial organism, including a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding a butadienepathway enzyme expressed in a sufficient amount to produce butadiene,the butadiene pathway including an erythrose-4-phosphate reductase, anerythritol-4-phospate cytidylyltransferase, a 4-(cytidine5′-diphospho)-erythritol kinase, an erythritol 2,4-cyclodiphosphatesynthase, a 1-hydroxy-2-butenyl 4-diphosphate synthase, a1-hydroxy-2-butenyl 4-diphosphate reductase, a butenyl 4-diphosphateisomerase, a butadiene synthase, an erythrose-4-phosphate kinase, anerythrose reductase or an erythritol kinase (FIG. 3). In one aspect, thenon-naturally occurring microbial organism includes a microbial organismhaving a butadiene pathway having at least one exogenous nucleic acidencoding butadiene pathway enzymes expressed in a sufficient amount toproduce butadiene, the butadiene pathway including anerythrose-4-phosphate reductase, an erythritol-4-phospatecytidylyltransferase, a 4-(cytidine 5′-diphospho)-erythritol kinase, anerythritol 2,4-cyclodiphosphate synthase, a 1-hydroxy-2-butenyl4-diphosphate synthase, a 1-hydroxy-2-butenyl 4-diphosphate reductaseand a butadiene synthase (FIG. 3, steps A-F, and H). In one aspect, thenon-naturally occurring microbial organism includes a microbial organismhaving a butadiene pathway having at least one exogenous nucleic acidencoding butadiene pathway enzymes expressed in a sufficient amount toproduce butadiene, the butadiene pathway including anerythrose-4-phosphate reductase, an erythritol-4-phospatecytidylyltransferase, a 4-(cytidine 5′-diphospho)-erythritol kinase, anerythritol 2,4-cyclodiphosphate synthase, a 1-hydroxy-2-butenyl4-diphosphate synthase, a 1-hydroxy-2-butenyl 4-diphosphate reductase, abutenyl 4-diphosphate isomerase and butadiene synthase (FIG. 3, stepsA-H). In one aspect, the non-naturally occurring microbial organismincludes a microbial organism having a butadiene pathway having at leastone exogenous nucleic acid encoding butadiene pathway enzymes expressedin a sufficient amount to produce butadiene, the butadiene pathwayincluding an erythritol-4-phospate cytidylyltransferase, a 4-(cytidine5′-diphospho)-erythritol kinase, an erythritol 2,4-cyclodiphosphatesynthase, a 1-hydroxy-2-butenyl 4-diphosphate synthase, a1-hydroxy-2-butenyl 4-diphosphate reductase, a butadiene synthase, anerythrose-4-phosphate kinase, an erythrose reductase and a erythritolkinase (FIG. 3, steps I, J, K, B-F, H). In one aspect, the non-naturallyoccurring microbial organism includes a microbial organism having abutadiene pathway having at least one exogenous nucleic acid encodingbutadiene pathway enzymes expressed in a sufficient amount to producebutadiene, the butadiene pathway including an erythritol-4-phospatecytidylyltransferase, a 4-(cytidine 5′-diphospho)-erythritol kinase, anerythritol 2,4-cyclodiphosphate synthase, a 1-hydroxy-2-butenyl4-diphosphate synthase, a 1-hydroxy-2-butenyl 4-diphosphate reductase, abutenyl 4-diphosphate isomerase, a butadiene synthase, anerythrose-4-phosphate kinase, an erythrose reductase and an erythritolkinase (FIG. 3, steps I, J, K, B-H).

In some embodiments, the invention provides a non-naturally occurringmicrobial organism, including a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding a butadienepathway enzyme expressed in a sufficient amount to produce butadiene,the butadiene pathway including a malonyl-CoA:acetyl-CoAacyltransferase, a 3-oxoglutaryl-CoA reductase (ketone-reducing), a3-hydroxyglutaryl-CoA reductase (aldehyde forming), a3-hydroxy-5-oxopentanoate reductase, a 3,5-dihydroxypentanoate kinase, a3-hydroxy-5-phosphonatooxypentanoate kinase, a3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthase,a 3-hydroxyglutaryl-CoA reductase (alcohol forming), a 3-oxoglutaryl-CoAreductase (aldehyde forming), a 3,5-dioxopentanoate reductase (ketonereducing), a 3,5-dioxopentanoate reductase (aldehyde reducing), a5-hydroxy-3-oxopentanoate reductase or a 3-oxo-glutaryl-CoA reductase(CoA reducing and alcohol forming) (FIG. 4). In one aspect, thenon-naturally occurring microbial organism includes a microbial organismhaving a butadiene pathway having at least one exogenous nucleic acidencoding butadiene pathway enzymes expressed in a sufficient amount toproduce butadiene, the butadiene pathway including amalonyl-CoA:acetyl-CoA acyltransferase, a 3-oxoglutaryl-CoA reductase(ketone-reducing), a 3-hydroxyglutaryl-CoA reductase (aldehyde forming),a 3-hydroxy-5-oxopentanoate reductase, a 3,5-dihydroxypentanoate kinase,a 3-hydroxy-5-phosphonatooxypentanoate kinase, a3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase and a butadienesynthase (FIG. 4, steps A-I). In one aspect, the non-naturally occurringmicrobial organism includes a microbial organism having a butadienepathway having at least one exogenous nucleic acid encoding butadienepathway enzymes expressed in a sufficient amount to produce butadiene,the butadiene pathway including a malonyl-CoA:acetyl-CoAacyltransferase, a 3,5-dihydroxypentanoate kinase, a3-hydroxy-5-phosphonatooxypentanoate kinase, a3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthase,a 3-oxoglutaryl-CoA reductase (aldehyde forming), a 3,5-dioxopentanoatereductase (aldehyde reducing) and a 5-hydroxy-3-oxopentanoate reductase.(FIG. 4, steps A, K, M, N, E, F, G, H, I). In one aspect, thenon-naturally occurring microbial organism includes a microbial organismhaving a butadiene pathway having at least one exogenous nucleic acidencoding butadiene pathway enzymes expressed in a sufficient amount toproduce butadiene, the butadiene pathway including amalonyl-CoA:acetyl-CoA acyltransferase, a 3-hydroxy-5-oxopentanoatereductase, a 3,5-dihydroxypentanoate kinase, a3-Hydroxy-5-phosphonatooxypentanoate kinase, a3-Hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthase,a 3-oxoglutaryl-CoA reductase (aldehyde forming) and a3,5-dioxopentanoate reductase (ketone reducing). (FIG. 4, steps A, K, L,D, E, F, G, H, I). In one aspect, the non-naturally occurring microbialorganism includes a microbial organism having a butadiene pathway havingat least one exogenous nucleic acid encoding butadiene pathway enzymesexpressed in a sufficient amount to produce butadiene, the butadienepathway including a malonyl-CoA:acetyl-CoA acyltransferase, a3,5-dihydroxypentanoate kinase, a 3-hydroxy-5-phosphonatooxypentanoatekinase, a 3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthase,a 5-hydroxy-3-oxopentanoate reductase and a 3-oxo-glutaryl-CoA reductase(CoA reducing and alcohol forming). (FIG. 4, steps A, O, N, E, F, G, H,I). In one aspect, the non-naturally occurring microbial organismincludes a microbial organism having a butadiene pathway having at leastone exogenous nucleic acid encoding butadiene pathway enzymes expressedin a sufficient amount to produce butadiene, the butadiene pathwayincluding a malonyl-CoA:acetyl-CoA acyltransferase, a 3-oxoglutaryl-CoAreductase (ketone-reducing), a 3,5-dihydroxypentanoate kinase, a3-hydroxy-5-phosphonatooxypentanoate kinase, a3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthaseand a 3-hydroxyglutaryl-CoA reductase (alcohol forming). (FIG. 4, stepsA, B, J, E, F, G, H, I).

In an additional embodiment, the invention provides a non-naturallyoccurring microbial organism having a butadiene pathway, wherein thenon-naturally occurring microbial organism comprises at least oneexogenous nucleic acid encoding an enzyme or protein that converts asubstrate to a product selected from the group consisting of acetyl-CoAto acetoacetyl-CoA, acetoacetyl-CoA to 3-hydroxybutyryl-CoA,3-hydroxybutyryl-CoA to crotonyl-CoA, crotonyl-CoA to crotonaldehyde,crotonaldehyde to crotyl alcohol, crotyl alcohol to 2-betenyl-phosphate,2-betenyl-phosphate to 2-butenyl-4-diphosphate, 2-butenyl-4-diphosphateto butadiene, erythrose-4-phosphate to erythritol-4-phosphate,erythritol-4-phosphate to 4-(cytidine 5′-diphospho)-erythritol,4-(cytidine 5′-diphospho)-erythritol to 2-phospho-4-(cytidine5′-diphospho)-erythritol, 2-phospho-4-(cytidine 5′-diphospho)-erythritolto erythritol-2,4-cyclodiphosphate, erythritol-2,4-cyclodiphosphate to1-hydroxy-2-butenyl 4-diphosphate, 1-hydroxy-2-butenyl 4-diphosphate tobutenyl 4-diphosphate, butenyl 4-diphosphate to 2-butenyl 4-diphosphate,1-hydroxy-2-butenyl 4-diphosphate to 2-butenyl 4-diphosphate, 2-butenyl4-diphosphate to butadiene, malonyl-CoA and acetyl-CoA to3-oxoglutaryl-CoA, 3-oxoglutaryl-CoA to 3-hydroxyglutaryl-CoA to3-hydroxy-5-oxopentanoate, 3-hydroxy-5-oxopentanoate to 3,5-dihydroxypentanoate, 3,5-dihydroxy pentanoate to3-hydroxy-5-phosphonatooxypentanoate,3-hydroxy-5-phosphonatooxypentanoate to3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoate,3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoate to butenyl4-biphosphate, glutaconyl-CoA to crotonyl-CoA, glutaryl-CoA tocrotonyl-CoA, 3-aminobutyryl-CoA to crotonyl-CoA, 4-hydroxybutyryl-CoAto crotonyl-CoA, crotonyl-CoA to crotonate, crotonate to crotonaldehyde,crotonyl-CoA to crotyl alcohol, crotyl alcohol to2-butenyl-4-diphosphate, erythrose-4-phosphate to erythrose, erythroseto erythritol, erythritol to erythritol-4-phosphate, 3-oxoglutaryl-CoAto 3,5-dioxopentanoate, 3,5-dioxopentanoate to5-hydroxy-3-oxopentanoate, 5-hydroxy-3-oxopentanoate to3,5-dihydroxypentanoate, 3-oxoglutaryl-CoA to 5-hydroxy-3-oxopentanoate,3,5-dioxopentanoate to 3-hydroxy-5-oxopentanoate and3-hydroxyglutaryl-CoA to 3,5-dihydroxypentanoate. One skilled in the artwill understand that these are merely exemplary and that any of thesubstrate-product pairs disclosed herein suitable to produce a desiredproduct and for which an appropriate activity is available for theconversion of the substrate to the product can be readily determined byone skilled in the art based on the teachings herein. Thus, theinvention provides a non-naturally occurring microbial organismcontaining at least one exogenous nucleic acid encoding an enzyme orprotein, where the enzyme or protein converts the substrates andproducts of a butadiene pathway, such as that shown in FIGS. 2-4.

While generally described herein as a microbial organism that contains abutadiene pathway, it is understood that the invention additionallyprovides a non-naturally occurring microbial organism comprising atleast one exogenous nucleic acid encoding a butadiene pathway enzymeexpressed in a sufficient amount to produce an intermediate of abutadiene pathway. For example, as disclosed herein, a butadiene pathwayis exemplified in FIGS. 2-4. Therefore, in addition to a microbialorganism containing a butadiene pathway that produces butadiene, theinvention additionally provides a non-naturally occurring microbialorganism comprising at least one exogenous nucleic acid encoding abutadiene pathway enzyme, where the microbial organism produces abutadiene pathway intermediate, for example, acetoacetyl-CoA,3-hydroxybutyryl-CoA, crotonyl-CoA, crotonaldehyde, crotyl alcohol,2-betenyl-phosphate, 2-butenyl-4-diphosphate, erythritol-4-phosphate,4-(cytidine 5′-diphospho)-erythritol, 2-phospho-4-(cytidine5′-diphospho)-erythritol, erythritol-2,4-cyclodiphosphate,1-hydroxy-2-butenyl 4-diphosphate, butenyl 4-diphosphate, 2-butenyl4-diphosphate, 3-oxoglutaryl-CoA, 3-hydroxyglutaryl-CoA,3-hydroxy-5-oxopentanoate, 3,5-dihydroxy pentanoate,3-hydroxy-5-phosphonatooxypentanoate,3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoate, crotonate,erythrose, erythritol, 3,5-dioxopentanoate or 5-hydroxy-3-oxopentanoate.

It is understood that any of the pathways disclosed herein, as describedin the Examples and exemplified in the Figures, including the pathwaysof FIGS. 2-4, can be utilized to generate a non-naturally occurringmicrobial organism that produces any pathway intermediate or product, asdesired. As disclosed herein, such a microbial organism that produces anintermediate can be used in combination with another microbial organismexpressing downstream pathway enzymes to produce a desired product.However, it is understood that a non-naturally occurring microbialorganism that produces a butadiene pathway intermediate can be utilizedto produce the intermediate as a desired product.

In some embodiments, access to butadiene can be accomplished bybiosynthetic production of crotyl alcohol and subsequent chemicaldehydration to butadiene. In some embodiments, the invention provides aprocess for the production of butadiene that includes (a) culturing byfermentation in a sufficient amount of nutrients and media anon-naturally occurring microbial organism that produces crotyl alcohol;and (b) converting crotyl alcohol produced by culturing thenon-naturally occurring microbial organism to butadiene.

The dehydration of alcohols are known in the art and can include variousthermal processes, both catalyzed and non-catalyzed. In someembodiments, a catalyzed thermal dehydration employs a metal oxidecatalyst or silica. In some embodiments, step (b) of the process isperformed by chemical dehydration in the presence of a catalyst. Forexample, it has been indicated that crotyl alcohol can be dehydratedover bismuth molybdate (Adams, C. R. J. Catal. 10:355-361, 1968) toafford 1,3-butadiene.

Dehydration can be achieved via activation of the alcohol group andsubsequent elimination by standard elimination mechanisms such as E1 orE2 elimination. Activation can be achieved by way of conversion of thealcohol group to a halogen such as iodide, chloride, or bromide.Activation can also be accomplished by way of a sulfonyl, phosphate orother activating functionality that convert the alcohol into a goodleaving group. In some embodiments, the activating group is a sulfate orsulfate ester selected from a tosylate, a mesylate, a nosylate, abrosylate, and a triflate. In some embodiments, the leaving group is aphosphate or phosphate ester. In some such embodiments, the dehydratingagent is phosphorus pentoxide.

In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize non-naturally occurringmicrobial organism that include a crotyl alcohol pathway having at leastone exogenous nucleic acid encoding a crotyl alcohol pathway enzymeexpressed in a sufficient amount to produce crotyl alcohol. The crotylalcohol pathway includes an acetyl-CoA:acetyl-CoA acyltransferase, anacetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, acrotonyl-CoA reductase (aldehyde forming), a crotonaldehyde reductase(alcohol forming), a crotonyl-CoA hydrolase, synthetase, or transferase,a crotonate reductase, a crotonyl-CoA reductase (alcohol forming), aglutaconyl-CoA decarboxylase, a glutaryl-CoA dehydrogenase, a3-aminobutyryl-CoA deaminase, or a 4-hydroxybutyryl-CoA dehydratase.

In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism thatincludes two exogenous nucleic acids each encoding a crotyl alcoholpathway enzyme. In some embodiments, processes of the invention thatrely on bioproduction of crotyl alcohol utilize a microbial organismthat includes three exogenous nucleic acids each encoding a crotylalcohol pathway enzyme. In some embodiments, processes of the inventionthat rely on bioproduction of crotyl alcohol utilize a microbialorganism that includes four exogenous nucleic acids each encoding acrotyl alcohol pathway enzyme.

In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having acrotyl alcohol pathway that includes an acetyl-CoA:acetyl-CoAacyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoAdehydratase, a crotonyl-CoA reductase (aldehyde forming), and acrotonaldehyde reductase (alcohol forming). In some embodiments,processes of the invention that rely on bioproduction of crotyl alcoholutilize a microbial organism having a crotyl alcohol pathway thatincludes an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoAreductase, a 3-hydroxybutyryl-CoA dehydratase, and a crotonyl-CoAreductase (alcohol forming). In some embodiments, processes of theinvention that rely on bioproduction of crotyl alcohol utilize amicrobial organism having a crotyl alcohol pathway that includes anacetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a3-hydroxybutyryl-CoA dehydratase, a crotonaldehyde reductase (alcoholforming), a crotonyl-CoA hydrolase, synthetase or transferase and acrotonate reductase.

In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having acrotyl alcohol pathway that includes a glutaconyl-CoA decarboxylase, acrotonyl-CoA reductase (aldehyde forming), and a crotonaldehydereductase (alcohol forming). In some embodiments, processes of theinvention that rely on bioproduction of crotyl alcohol utilize amicrobial organism having a crotyl alcohol pathway that includes aglutaconyl-CoA decarboxylase and crotonyl-CoA reductase (alcoholforming). In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having acrotyl alcohol pathway that includes a glutaconyl-CoA decarboxylase, acrotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase,synthetase, or transferase and a crotonate reductase. In someembodiments, processes of the invention that rely on bioproduction ofcrotyl alcohol utilize a microbial organism having a crotyl alcoholpathway that includes a 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoAreductase (aldehyde forming), a crotonaldehyde reductase (alcoholforming), and a glutaconyl-CoA decarboxylase.

In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having acrotyl alcohol pathway that includes a glutaryl-CoA dehydrogenase, acrotonyl-CoA reductase (aldehyde forming), and a crotonaldehydereductase (alcohol forming). In some embodiments, processes of theinvention that rely on bioproduction of crotyl alcohol utilize amicrobial organism having a crotyl alcohol pathway that includes aglutaryl-CoA dehydrogenase and crotonyl-CoA reductase (alcohol forming).In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having acrotyl alcohol pathway that includes a glutaryl-CoA dehydrogenase, acrotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase,synthetase, or transferase and a crotonate reductase. In someembodiments, processes of the invention that rely on bioproduction ofcrotyl alcohol utilize a microbial organism having a crotyl alcoholpathway that includes a 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoAreductase (aldehyde forming), a crotonaldehyde reductase (alcoholforming), and a glutaryl-CoA dehydrogenase.

In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having acrotyl alcohol pathway that includes a 3-aminobutyryl-CoA deaminase, acrotonyl-CoA reductase (aldehyde forming), and a crotonaldehydereductase (alcohol forming). In some embodiments, processes of theinvention that rely on bioproduction of crotyl alcohol utilize amicrobial organism having a crotyl alcohol pathway that includes a3-aminobutyryl-CoA deaminase and crotonyl-CoA reductase (alcoholforming). In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having acrotyl alcohol pathway that includes a 3-aminobutyryl-CoA deaminase, acrotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase,synthetase or transferase and a crotonate reductase. In someembodiments, processes of the invention that rely on bioproduction ofcrotyl alcohol utilize a microbial organism having a crotyl alcoholpathway that includes a 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoAreductase (aldehyde forming), a crotonaldehyde reductase (alcoholforming), and a 3-aminobutyryl-CoA deaminase.

In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having acrotyl alcohol pathway that includes a 4-hydroxybutyryl-CoA dehydratase,a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehydereductase (alcohol forming). In some embodiments, processes of theinvention that rely on bioproduction of crotyl alcohol utilize amicrobial organism having a crotyl alcohol pathway that includes a4-hydroxybutyryl-CoA dehydratase and crotonyl-CoA reductase (alcoholforming). In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having acrotyl alcohol pathway that includes a 4-hydroxybutyryl-CoA dehydratase,a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase,synthetase or transferase and a crotonate reductase. In someembodiments, processes of the invention that rely on bioproduction ofcrotyl alcohol utilize a microbial organism having a crotyl alcoholpathway that includes a 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoAreductase (aldehyde forming), a crotonaldehyde reductase (alcoholforming), and a 4-hydroxybutyryl-CoA dehydratase.

In some embodiments, processes of the invention that rely onbioproduction of crotyl alcohol utilize a microbial organism having atleast one exogenous nucleic acid is a heterologous nucleic acid. In someembodiments, processes of the invention that rely on bioproduction ofcrotyl alcohol utilize a non-naturally occurring microbial organism isin a substantially anaerobic culture medium.

Given the teachings and guidance provided herein, those skilled in theart will understand that other biosynthetic intermediates in a butadienepathway can be targeted in further chemoenzymatic routes to1,3-butadiene. For example, it has been indicated that crotonaldehyde isconverted to 1,3-butadiene in the presence of ethanol over a silicacatalyst (Toussaint et al., Ind. Eng. Chem., 39(2):120-125, (1947)). Insome embodiments, a process for the production of 1,3-butadiene includesa) culturing by fermentation in a sufficient amount of nutrients andmedia a non-naturally occurring microbial organism that producescrotonaldehyde; and (b) converting crotonaldehyde produced by culturingthe non-naturally occurring microbial organism to butadiene. In somesuch chemoenzymatic processes of the invention, crotonaldehyde andethanol can both be provided as fermentation products from a singlenon-naturally occurring organism, or from two separate organisms. Thetwo fermentation products can be converted to 1,3-butadiene as describedabove using silica catalyst.

The invention is described herein with general reference to themetabolic reaction, reactant or product thereof, or with specificreference to one or more nucleic acids or genes encoding an enzymeassociated with or catalyzing, or a protein associated with, thereferenced metabolic reaction, reactant or product. Unless otherwiseexpressly stated herein, those skilled in the art will understand thatreference to a reaction also constitutes reference to the reactants andproducts of the reaction. Similarly, unless otherwise expressly statedherein, reference to a reactant or product also references the reaction,and reference to any of these metabolic constituents also references thegene or genes encoding the enzymes that catalyze or proteins involved inthe referenced reaction, reactant or product. Likewise, given the wellknown fields of metabolic biochemistry, enzymology and genomics,reference herein to a gene or encoding nucleic acid also constitutes areference to the corresponding encoded enzyme and the reaction itcatalyzes or a protein associated with the reaction as well as thereactants and products of the reaction.

As disclosed herein, the intermediats crotanate; 3,5-dioxopentanoate,5-hydroxy-3-oxopentanoate, 3-hydroxy-5-oxopentanoate, 3-oxoglutaryl-CoAand 3-hydroxyglutaryl-CoA, as well as other intermediates, arecarboxylic acids, which can occur in various ionized forms, includingfully protonated, partially protonated, and fully deprotonated forms.Accordingly, the suffix “-ate,” or the acid form, can be usedinterchangeably to describe both the free acid form as well as anydeprotonated form, in particular since the ionized form is known todepend on the pH in which the compound is found. It is understood thatcarboxylate products or intermediates includes ester forms ofcarboxylate products or pathway intermediates, such as O-carboxylate andS-carboxylate esters. O- and S-carboxylates can include lower alkyl,that is C1 to C6, branched or straight chain carboxylates. Some such O-or S-carboxylates include, without limitation, methyl, ethyl, n-propyl,n-butyl, i-propyl, sec-butyl, and tert-butyl, pentyl, hexyl O- orS-carboxylates, any of which can further possess an unsaturation,providing for example, propenyl, butenyl, pentyl, and hexenyl O- orS-carboxylates. O-carboxylates can be the product of a biosyntheticpathway. Exemplary O-carboxylates accessed via biosynthetic pathways caninclude, without limitation: methyl crotanate;methyl-3,5-dioxopentanoate; methyl-5-hydroxy-3-oxopentanoate;methyl-3-hydroxy-5-oxopentanoate; 3-oxoglutaryl-CoA, methyl ester;3-hydroxyglutaryl-CoA, methyl ester; ethyl crotanate;ethyl-3,5-dioxopentanoate; ethyl-5-hydroxy-3-xopentanoate;ethyl-3-hydroxy-5-oxopentanoate; 3-oxoglutaryl-CoA, ethyl ester;3-hydroxyglutaryl-CoA, ethyl ester; n-propyl crotanate;n-propyl-3,5-dioxopentanoate; n-propyl-5-hydroxy-3-oxopentanoate;n-propyl-3-hydroxy-5-oxopentanoate; 3-oxoglutaryl-CoA, n-propyl ester;and 3-hydroxyglutaryl-CoA, n-propyl ester. Other biosyntheticallyaccessible O-carboxylates can include medium to long chain groups, thatis C7-C22, O-carboxylate esters derived from fatty alcohols, suchheptyl, octyl, nonyl, decyl, undecyl, lauryl, tridecyl, myristyl,pentadecyl, cetyl, palmitolyl, heptadecyl, stearyl, nonadecyl,arachidyl, heneicosyl, and behenyl alcohols, any one of which can beoptionally branched and/or contain unsaturations. O-carboxylate esterscan also be accessed via a biochemical or chemical process, such asesterification of a free carboxylic acid product or transesterificationof an O- or S-carboxylate. S-carboxylates are exemplified by CoAS-esters, cysteinyl S-esters, alkylthioesters, and various aryl andheteroaryl thioesters.

The non-naturally occurring microbial organisms of the invention can beproduced by introducing expressible nucleic acids encoding one or moreof the enzymes or proteins participating in one or more butadienebiosynthetic pathways. Depending on the host microbial organism chosenfor biosynthesis, nucleic acids for some or all of a particularbutadiene biosynthetic pathway can be expressed. For example, if achosen host is deficient in one or more enzymes or proteins for adesired biosynthetic pathway, then expressible nucleic acids for thedeficient enzyme(s) or protein(s) are introduced into the host forsubsequent exogenous expression. Alternatively, if the chosen hostexhibits endogenous expression of some pathway genes, but is deficientin others, then an encoding nucleic acid is needed for the deficientenzyme(s) or protein(s) to achieve butadiene biosynthesis. Thus, anon-naturally occurring microbial organism of the invention can beproduced by introducing exogenous enzyme or protein activities to obtaina desired biosynthetic pathway or a desired biosynthetic pathway can beobtained by introducing one or more exogenous enzyme or proteinactivities that, together with one or more endogenous enzymes orproteins, produces a desired product such as butadiene.

Host microbial organisms can be selected from, and the non-naturallyoccurring microbial organisms generated in, for example, bacteria,yeast, fungus or any of a variety of other microorganisms applicable tofermentation processes. Exemplary bacteria include species selected fromEscherichia coli, Klebsiella oxytoca, Anaerobiospirillumsucciniciproducens, Actinobacillus succinogenes, Mannheimiasucciniciproducens, Rhizobium etli, Bacillus subtilis, Corynebacteriumglutamicum, Gluconobacter oxydans, Zymomonas mobilis, Lactococcuslactis, Lactobacillus plantarum, Streptomyces coelicolor, Clostridiumacetobutylicum, Pseudomonas fluorescens, and Pseudomonas putida.Exemplary yeasts or fungi include species selected from Saccharomycescerevisiae, Schizosaccharomyces pombe, Kluyveromyces lactis,Kluyveromyces marxianus, Aspergillus terreus, Aspergillus niger, Pichiapastoris, Rhizopus arrhizus, Rhizobus oryzae, Yarrowia lipolytica, andthe like. E. coli is a particularly useful host organism since it is awell characterized microbial organism suitable for genetic engineering.Other particularly useful host organisms include yeast such asSaccharomyces cerevisiae. It is understood that any suitable microbialhost organism can be used to introduce metabolic and/or geneticmodifications to produce a desired product.

Depending on the butadiene biosynthetic pathway constituents of aselected host microbial organism, the non-naturally occurring microbialorganisms of the invention will include at least one exogenouslyexpressed butadiene pathway-encoding nucleic acid and up to all encodingnucleic acids for one or more butadiene biosynthetic pathways. Forexample, butadiene biosynthesis can be established in a host deficientin a pathway enzyme or protein through exogenous expression of thecorresponding encoding nucleic acid. In a host deficient in all enzymesor proteins of a butadiene pathway, exogenous expression of all enzymeor proteins in the pathway can be included, although it is understoodthat all enzymes or proteins of a pathway can be expressed even if thehost contains at least one of the pathway enzymes or proteins. Forexample, exogenous expression of all enzymes or proteins in a pathwayfor production of butadiene can be included, such as anacetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehydeforming), a crotonaldehyde reductase (alcohol forming), a crotyl alcoholkinase, a 2-butenyl-4-phosphate kinase and a butadiene synthase (FIG. 2,steps A-H).

Given the teachings and guidance provided herein, those skilled in theart will understand that the number of encoding nucleic acids tointroduce in an expressible form will, at least, parallel the butadienepathway deficiencies of the selected host microbial organism. Therefore,a non-naturally occurring microbial organism of the invention can haveone, two, three, four, five, six, seven, eight, nine or ten, up to allnucleic acids encoding the enzymes or proteins constituting a butadienebiosynthetic pathway disclosed herein. In some embodiments, thenon-naturally occurring microbial organisms also can include othergenetic modifications that facilitate or optimize butadiene biosynthesisor that confer other useful functions onto the host microbial organism.One such other functionality can include, for example, augmentation ofthe synthesis of one or more of the butadiene pathway precursors such asacetyl-CoA, glutaconyl-CoA, glutaryl-CoA, 3-aminobutyryl-CoA,4-hydroxybutyryl-CoA, erythrose-4-phosphate or malonyl-CoA.

Generally, a host microbial organism is selected such that it producesthe precursor of a butadiene pathway, either as a naturally producedmolecule or as an engineered product that either provides de novoproduction of a desired precursor or increased production of a precursornaturally produced by the host microbial organism. For example,acetyl-CoA, glutaconyl-CoA, glutaryl-CoA, 3-aminobutyryl-CoA,4-hydroxybutyryl-CoA, erythrose-4-phosphate or malonyl-CoA are producednaturally in a host organism such as E. coli. A host organism can beengineered to increase production of a precursor, as disclosed herein.In addition, a microbial organism that has been engineered to produce adesired precursor can be used as a host organism and further engineeredto express enzymes or proteins of a butadiene pathway.

In some embodiments, a non-naturally occurring microbial organism of theinvention is generated from a host that contains the enzymaticcapability to synthesize butadiene. In this specific embodiment it canbe useful to increase the synthesis or accumulation of a butadienepathway product to, for example, drive butadiene pathway reactionstoward butadiene production. Increased synthesis or accumulation can beaccomplished by, for example, overexpression of nucleic acids encodingone or more of the above-described butadiene pathway enzymes orproteins. Over expression the enzyme or enzymes and/or protein orproteins of the butadiene pathway can occur, for example, throughexogenous expression of the endogenous gene or genes, or throughexogenous expression of the heterologous gene or genes. Therefore,naturally occurring organisms can be readily generated to benon-naturally occurring microbial organisms of the invention, forexample, producing butadiene, through overexpression of one, two, three,four, five, six, seven, eight, nine, or ten, that is, up to all nucleicacids encoding butadiene biosynthetic pathway enzymes or proteins. Inaddition, a non-naturally occurring organism can be generated bymutagenesis of an endogenous gene that results in an increase inactivity of an enzyme in the butadiene biosynthetic pathway.

In particularly useful embodiments, exogenous expression of the encodingnucleic acids is employed. Exogenous expression confers the ability tocustom tailor the expression and/or regulatory elements to the host andapplication to achieve a desired expression level that is controlled bythe user. However, endogenous expression also can be utilized in otherembodiments such as by removing a negative regulatory effector orinduction of the gene's promoter when linked to an inducible promoter orother regulatory element. Thus, an endogenous gene having a naturallyoccurring inducible promoter can be up-regulated by providing theappropriate inducing agent, or the regulatory region of an endogenousgene can be engineered to incorporate an inducible regulatory element,thereby allowing the regulation of increased expression of an endogenousgene at a desired time. Similarly, an inducible promoter can be includedas a regulatory element for an exogenous gene introduced into anon-naturally occurring microbial organism.

It is understood that, in methods of the invention, any of the one ormore exogenous nucleic acids can be introduced into a microbial organismto produce a non-naturally occurring microbial organism of theinvention. The nucleic acids can be introduced so as to confer, forexample, a butadiene biosynthetic pathway onto the microbial organism.Alternatively, encoding nucleic acids can be introduced to produce anintermediate microbial organism having the biosynthetic capability tocatalyze some of the required reactions to confer butadiene biosyntheticcapability. For example, a non-naturally occurring microbial organismhaving a butadiene biosynthetic pathway can comprise at least twoexogenous nucleic acids encoding desired enzymes or proteins, such asthe combination of a crotyl alcohol kinase and a butadiene synthase, oralternatively a 4-(cytidine 5′-diphospho)-erythritol kinase andbutadiene synthase, or alternatively a 1-hydroxy-2-butenyl 4-diphosphatesynthase and a butadiene synthase, or alternatively a3-hydroxy-5-phosphonatooxypentanoate kinase and a butadiene synthase, oralternatively a crotonyl-CoA hydrolase and a crotyl alcoholdiphosphokinase, or alternatively a an erythrose reductase and butadienesynthase or alternatively a 3-oxo-glutaryl-CoA reductase (CoA reducingand alcohol forming) and3-Hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, and the like. Thus, it is understood that any combinationof two or more enzymes or proteins of a biosynthetic pathway can beincluded in a non-naturally occurring microbial organism of theinvention. Similarly, it is understood that any combination of three ormore enzymes or proteins of a biosynthetic pathway can be included in anon-naturally occurring microbial organism of the invention, forexample, a crotyl alcohol kinase, a 2-butenyl-4-phosphate kinase and abutadiene synthase, or alternatively a 1-hydroxy-2-butenyl 4-diphosphatesynthase, a 1-hydroxy-2-butenyl 4-diphosphate reductase, and butadienesynthase, or alternatively a 3-oxoglutaryl-CoA reductase, a3-hydroxy-5-oxopentanoate reductase, and a butadiene synthase, oralternatively an acetyl-CoA:acetyl-CoA acyltransferase, a crotyl alcoholkinase and a butadiene synthase, or alternatively a glutaconyl-CoAdecarboxylase, a crotonyl-CoA reductase (alcohol forming), and a crotylalcohol diphosphokinase, or alternatively a an erythrose-4-phosphatekinase, a 4-(cytidine 5′-diphospho)-erythritol kinase and a1-hydroxy-2-butenyl 4-diphosphate synthase, or alternatively a3,5-dioxopentanoate reductase (aldehyde reducing), a butenyl4-diphosphate isomerase, and a butadiene synthase, and so forth, asdesired, so long as the combination of enzymes and/or proteins of thedesired biosynthetic pathway results in production of the correspondingdesired product. Similarly, any combination of four, such as acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase and a butadiene synthase, or alternativelya 1-hydroxy-2-butenyl 4-diphosphate synthase, a 1-hydroxy-2-butenyl4-diphosphate reductase, a butenyl 4-diphosphate isomerase and butadienesynthase, or alternatively a 3-hydroxy-5-phosphonatooxypentanoatekinase, a 3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatekinase, a butenyl 4-diphosphate isomerase and a butadiene synthase, oralternatively an erythrose-4-phosphate reductase, anerythritol-4-phospate cytidylyltransferase, a 4-(cytidine5′-diphospho)-erythritol kinase and butadiene synthase, or alternativelya 3-aminobutyryl-CoA deaminase, a crotonyl-CoA reductase (alcoholforming), a crotyl alcohol diphosphokinase and a butadiene synthase, oralternatively an erythrose reductase, a 4-(cytidine5′-diphospho)-erythritol kinase, an erythritol 2,4-cyclodiphosphatesynthase and a 1-hydroxy-2-butenyl 4-diphosphate reductase, oralternatively a malonyl-CoA:acetyl-CoA acyltransferase, a3-hydroxyglutaryl-CoA reductase (alcohol forming), a butenyl4-diphosphate isomerase and a butadiene synthase, or more enzymes orproteins of a biosynthetic pathway as disclosed herein can be includedin a non-naturally occurring microbial organism of the invention, asdesired, so long as the combination of enzymes and/or proteins of thedesired biosynthetic pathway results in production of the correspondingdesired product.

In addition to the biosynthesis of butadiene as described herein, thenon-naturally occurring microbial organisms and methods of the inventionalso can be utilized in various combinations with each other and withother microbial organisms and methods well known in the art to achieveproduct biosynthesis by other routes. For example, one alternative toproduce butadiene other than use of the butadiene producers is throughaddition of another microbial organism capable of converting a butadienepathway intermediate to butadiene. One such procedure includes, forexample, the fermentation of a microbial organism that produces abutadiene pathway intermediate. The butadiene pathway intermediate canthen be used as a substrate for a second microbial organism thatconverts the butadiene pathway intermediate to butadiene. The butadienepathway intermediate can be added directly to another culture of thesecond organism or the original culture of the butadiene pathwayintermediate producers can be depleted of these microbial organisms by,for example, cell separation, and then subsequent addition of the secondorganism to the fermentation broth can be utilized to produce the finalproduct without intermediate purification steps.

In other embodiments, the non-naturally occurring microbial organismsand methods of the invention can be assembled in a wide variety ofsubpathways to achieve biosynthesis of, for example, butadiene. In theseembodiments, biosynthetic pathways for a desired product of theinvention can be segregated into different microbial organisms, and thedifferent microbial organisms can be co-cultured to produce the finalproduct. In such a biosynthetic scheme, the product of one microbialorganism is the substrate for a second microbial organism until thefinal product is synthesized. For example, the biosynthesis of butadienecan be accomplished by constructing a microbial organism that containsbiosynthetic pathways for conversion of one pathway intermediate toanother pathway intermediate or the product. Alternatively, butadienealso can be biosynthetically produced from microbial organisms throughco-culture or co-fermentation using two organisms in the same vessel,where the first microbial organism produces a butadiene intermediate andthe second microbial organism converts the intermediate to butadiene.

Given the teachings and guidance provided herein, those skilled in theart will understand that a wide variety of combinations and permutationsexist for the non-naturally occurring microbial organisms and methods ofthe invention together with other microbial organisms, with theco-culture of other non-naturally occurring microbial organisms havingsubpathways and with combinations of other chemical and/or biochemicalprocedures well known in the art to produce butadiene.

Sources of encoding nucleic acids for a butadiene pathway enzyme orprotein can include, for example, any species where the encoded geneproduct is capable of catalyzing the referenced reaction. Such speciesinclude both prokaryotic and eukaryotic organisms including, but notlimited to, bacteria, including archaea and eubacteria, and eukaryotes,including yeast, plant, insect, animal, and mammal, including human.Exemplary species for such sources include, for example, Escherichiacoli, Acidaminococcus fermentans, Acinetobacter baylyi, Acinetobactercalcoaceticus, Acinetobacter sp. ADP1, Acinetobacter sp. Strain M-1,Aquifex aeolicus, Arabidopsis thaliana, Arabidopsis thaliana col,Arabidopsis thaliana col, Archaeoglobus fulgidus DSM 4304, Azoarcus sp.CIB, Bacillus cereus, Bacillus subtilis, Bos Taurus, Brucellamelitensis, Burkholderia ambifaria AMMD, Burkholderia phymatum,Campylobacter jejuni, Candida albicans, Candida magnoliae, Chloroflexusaurantiacus, Citrobacter youngae ATCC 29220, Clostridium acetobutylicum,Clostridium aminobutyricum, Clostridium beijerinckii, Clostridiumbeijerinckii NCIMB 8052, Clostridium beijerinckii NRRL B593, Clostridiumbotulinum C str. Eklund, Clostridium kluyveri, Clostridium kluyveri DSM555, Clostridium novyi NT, Clostridium propionicum, Clostridiumsaccharoperbutylacetonicum, Corynebacterium glutamicum ATCC 13032,Cupriavidus taiwanensis, Cyanobium PCC7001, Dictyostelium discoideumAX4, Enterococcus faecalis, Erythrobacter sp. NAP1, Escherichia coliK12, Escherichia coli str. K-12 substr. MG1655, Eubacterium rectale ATCC33656, Fusobacterium nucleatum, Fusobacterium nucleatum subsp. nucleatumATCC 25586, Geobacillus thermoglucosidasius, Haematococcus pluvialis,Haemophilus influenzae, Haloarcula marismortui ATCC 43049, Helicobacterpylori, Homo sapiens, Klebsiella pneumoniae, Lactobacillus plantarum,Leuconostoc mesenteroides, marine gamma proteobacterium HTCC2080,Metallosphaera sedula, Methanocaldococcus jannaschii, Mus musculus,Mycobacterium avium subsp. paratuberculosis K-10, Mycobacterium bovisBCG, Mycobacterium marinum M, Mycobacterium smegmatis MC2 155,Mycobacterium tuberculosis, Mycoplasma pneumoniae M129, Nocardiafarcinica IFM 10152, Nocardia iowensis (sp. NRRL 5646), Oryctolaguscuniculus, Paracoccus denitrificans, Penicillium chrysogenum, Populusalba, Populus tremula×Populus alba, Porphyromonas gingivalis,Porphyromonas gingivalis W83, Pseudomonas aeruginosa, Pseudomonasaeruginosa PA01, Pseudomonas fluorescens, Pseudomonas fluorescens Pf-5,Pseudomonas knackmussii (B13), Pseudomonas putida, Pseudomonas putidaE23, Pseudomonas putida KT2440, Pseudomonas sp, Pueraria Montana,Pyrobaculum aerophilum str. IM2, Pyrococcus furiosus, Ralstoniaeutropha, Ralstonia eutropha H16, Ralstonia eutropha H16, Ralstoniametallidurans, Rattus norvegicus, Rhodobacter spaeroides, Rhodococcusrubber, Rhodopseudomonas palustris, Roseburia intestinalis L1-82,Roseburia inulinivorans DSM 16841, Roseburia sp. A2-183, Roseiflexuscastenholzii, Saccharomyces cerevisiae, Saccharopolyspora rythraea NRRL2338, Salmonella enterica subsp. arizonae serovar, Salmonellatyphimurium, Schizosaccharomyces pombe, Simmondsia chinensis,Sinorhizobium meliloti, Staphylococcus, ureus, Streptococcus pneumoniae,Streptomyces coelicolor, Streptomyces griseus subsp. griseus, BRC 13350,Streptomyces sp. ACT-1, Sulfolobus acidocaldarius, Sulfolobus shibatae,Sulfolobus solfataricus, Sulfolobus tokodaii, Synechocystis sp. strainPCC6803, Syntrophus, ciditrophicus, Thermoanaerobacter brockii HTD4,Thermoanaerobacter tengcongensis MB4, Thermosynechococcus elongates,Thermotoga maritime MSB8, Thermus thermophilus, Thermus, hermophilusHB8, Trichomonas vaginalis G3, Trichosporonoides megachiliensis,Trypanosoma brucei, Tsukamurella paurometabola DSM 20162, Yersiniaintermedia ATCC 29909, Zoogloea ramigera, Zygosaccharomyces rouxii,Zymomonas mobilis, as well as other exemplary species disclosed hereinare available as source organisms for corresponding genes. However, withthe complete genome sequence available for now more than 550 species(with more than half of these available on public databases such as theNCBI), including 395 microorganism genomes and a variety of yeast,fungi, plant, and mammalian genomes, the identification of genesencoding the requisite butadiene biosynthetic activity for one or moregenes in related or distant species, including for example, homologues,orthologs, paralogs and nonorthologous gene displacements of knowngenes, and the interchange of genetic alterations between organisms isroutine and well known in the art. Accordingly, the metabolicalterations allowing biosynthesis of butadiene described herein withreference to a particular organism such as E. coli can be readilyapplied to other microorganisms, including prokaryotic and eukaryoticorganisms alike. Given the teachings and guidance provided herein, thoseskilled in the art will know that a metabolic alteration exemplified inone organism can be applied equally to other organisms.

In some instances, such as when an alternative butadiene biosyntheticpathway exists in an unrelated species, butadiene biosynthesis can beconferred onto the host species by, for example, exogenous expression ofa paralog or paralogs from the unrelated species that catalyzes asimilar, yet non-identical metabolic reaction to replace the referencedreaction. Because certain differences among metabolic networks existbetween different organisms, those skilled in the art will understandthat the actual gene usage between different organisms may differ.However, given the teachings and guidance provided herein, those skilledin the art also will understand that the teachings and methods of theinvention can be applied to all microbial organisms using the cognatemetabolic alterations to those exemplified herein to construct amicrobial organism in a species of interest that will synthesizebutadiene.

Methods for constructing and testing the expression levels of anon-naturally occurring butadiene-producing host can be performed, forexample, by recombinant and detection methods well known in the art.Such methods can be found described in, for example, Sambrook et al.,Molecular Cloning: A Laboratory Manual, Third Ed., Cold Spring HarborLaboratory, New York (2001); and Ausubel et al., Current Protocols inMolecular Biology, John Wiley and Sons, Baltimore, Md. (1999).

Exogenous nucleic acid sequences involved in a pathway for production ofbutadiene can be introduced stably or transiently into a host cell usingtechniques well known in the art including, but not limited to,conjugation, electroporation, chemical transformation, transduction,transfection, and ultrasound transformation. For exogenous expression inE. coli or other prokaryotic cells, some nucleic acid sequences in thegenes or cDNAs of eukaryotic nucleic acids can encode targeting signalssuch as an N-terminal mitochondrial or other targeting signal, which canbe removed before transformation into prokaryotic host cells, ifdesired. For example, removal of a mitochondrial leader sequence led toincreased expression in E. coli (Hoffmeister et al., J. Biol. Chem.280:4329-4338 (2005)). For exogenous expression in yeast or othereukaryotic cells, genes can be expressed in the cytosol without theaddition of leader sequence, or can be targeted to mitochondrion orother organelles, or targeted for secretion, by the addition of asuitable targeting sequence such as a mitochondrial targeting orsecretion signal suitable for the host cells. Thus, it is understoodthat appropriate modifications to a nucleic acid sequence to remove orinclude a targeting sequence can be incorporated into an exogenousnucleic acid sequence to impart desirable properties. Furthermore, genescan be subjected to codon optimization with techniques well known in theart to achieve optimized expression of the proteins.

An expression vector or vectors can be constructed to include one ormore butadiene biosynthetic pathway encoding nucleic acids asexemplified herein operably linked to expression control sequencesfunctional in the host organism. Expression vectors applicable for usein the microbial host organisms of the invention include, for example,plasmids, phage vectors, viral vectors, episomes and artificialchromosomes, including vectors and selection sequences or markersoperable for stable integration into a host chromosome. Additionally,the expression vectors can include one or more selectable marker genesand appropriate expression control sequences. Selectable marker genesalso can be included that, for example, provide resistance toantibiotics or toxins, complement auxotrophic deficiencies, or supplycritical nutrients not in the culture media. Expression controlsequences can include constitutive and inducible promoters,transcription enhancers, transcription terminators, and the like whichare well known in the art. When two or more exogenous encoding nucleicacids are to be co-expressed, both nucleic acids can be inserted, forexample, into a single expression vector or in separate expressionvectors. For single vector expression, the encoding nucleic acids can beoperationally linked to one common expression control sequence or linkedto different expression control sequences, such as one induciblepromoter and one constitutive promoter. The transformation of exogenousnucleic acid sequences involved in a metabolic or synthetic pathway canbe confirmed using methods well known in the art. Such methods include,for example, nucleic acid analysis such as Northern blots or polymerasechain reaction (PCR) amplification of mRNA, or immunoblotting forexpression of gene products, or other suitable analytical methods totest the expression of an introduced nucleic acid sequence or itscorresponding gene product. It is understood by those skilled in the artthat the exogenous nucleic acid is expressed in a sufficient amount toproduce the desired product, and it is further understood thatexpression levels can be optimized to obtain sufficient expression usingmethods well known in the art and as disclosed herein.

In some embodiments, the invention provides a method for producingbutadiene that includes culturing a non-naturally occurring microbialorganism, including a microbial organism having a butadiene pathway, thebutadiene pathway including at least one exogenous nucleic acid encodinga butadiene pathway enzyme expressed in a sufficient amount to producebutadiene, the butadiene pathway including an acetyl-CoA:acetyl-CoAacyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoAdehydratase, a crotonyl-CoA reductase (aldehyde forming), acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase, a crotonyl-CoAhydrolase, synthetase, or transferase, a crotonate reductase, acrotonyl-CoA reductase (alcohol forming), a glutaconyl-CoAdecarboxylase, a glutaryl-CoA dehydrogenase, a 3-aminobutyryl-CoAdeaminase, a 4-hydroxybutyryl-CoA dehydratase or a crotyl alcoholdiphosphokinase (FIG. 2). In one aspect, the method includes a microbialorganism having a butadiene pathway including an acetyl-CoA:acetyl-CoAacyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoAdehydratase, a crotonyl-CoA reductase (aldehyde forming), acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase and a butadiene synthase (FIG. 2, stepsA-H). In one aspect, the method includes a microbial organism having abutadiene pathway including an acetyl-CoA:acetyl-CoA acyltransferase, anacetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, a crotylalcohol kinase, a 2-butenyl-4-phosphate kinase, a butadiene synthase andcrotonyl-CoA reductase (alcohol forming) (FIG. 2, steps A-C, K, F, G,H). In one aspect, the method includes a microbial organism having abutadiene pathway including an acetyl-CoA:acetyl-CoA acyltransferase, anacetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, abutadiene synthase, a crotonyl-CoA reductase (alcohol forming) and acrotyl alcohol diphosphokinase (FIG. 2, steps A-C, K, P, H). In oneaspect, the method includes a microbial organism having a butadienepathway including an acetyl-CoA:acetyl-CoA acyltransferase, anacetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase, a crotonyl-CoAhydrolase, synthetase, or transferase and a crotonate reductase, (FIG.2, steps A-C, I, J, E, F, G, H). In one aspect, the method includes amicrobial organism having a butadiene pathway including anacetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a3-hydroxybutyryl-CoA dehydratase, a crotonaldehyde reductase (alcoholforming), a butadiene synthase, a crotonyl-CoA hydrolase, synthetase ortransferase, a crotonate reductase and a crotyl alcohol diphosphokinase(FIG. 2, steps A-C, I, J, E, P, H). In one aspect, the method includes amicrobial organism having a butadiene pathway including anacetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehydeforming), a crotonaldehyde reductase (alcohol forming), a butadienesynthase and a crotyl alcohol diphosphokinase (FIG. 2, steps A-E, P, H).In one aspect, the method includes a microbial organism having abutadiene pathway including a glutaconyl-CoA decarboxylase, acrotonyl-CoA reductase (aldehyde forming), a crotonaldehyde reductase(alcohol forming), a crotyl alcohol kinase, a 2-butenyl-4-phosphatekinase and a butadiene synthase (FIG. 2, steps L, D-H). In one aspect,the method includes a microbial organism having a butadiene pathwayincluding a glutaconyl-CoA decarboxylase, a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase and crotonyl-CoAreductase (alcohol forming) (FIG. 2, steps L, K, F, G, H). In oneaspect, the method includes a microbial organism having a butadienepathway including a glutaconyl-CoA decarboxylase, a butadiene synthase,a crotonyl-CoA reductase (alcohol forming) and a crotyl alcoholdiphosphokinase (FIG. 2, steps L, K, P, H). In one aspect, the methodincludes a microbial organism having a butadiene pathway including aglutaconyl-CoA decarboxylase, a crotonaldehyde reductase (alcoholforming), a crotyl alcohol kinase, a 2-butenyl-4-phosphate kinase, abutadiene synthase, a crotonyl-CoA hydrolase, synthetase, or transferaseand a crotonate reductase (FIG. 2, steps L, I, J, E, F, G, H). In oneaspect, the method includes a microbial organism having a butadienepathway including a glutaconyl-CoA decarboxylase, a crotonaldehydereductase (alcohol forming), a butadiene synthase, a crotonyl-CoAhydrolase, synthetase or transferase, a crotonate reductase and a crotylalcohol diphosphokinase (FIG. 2, steps L, I, J, E, P, H). In one aspect,the method includes a microbial organism having a butadiene pathwayincluding a 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase(aldehyde forming), a crotonaldehyde reductase (alcohol forming), abutadiene a glutaconyl-CoA decarboxylase and a crotyl alcoholdiphosphokinase (FIG. 2, steps L, C, D, E, P, H). In one aspect, themethod includes a microbial organism having a butadiene pathwayincluding a glutaryl-CoA dehydrogenase, a crotonyl-CoA reductase(aldehyde forming), a crotonaldehyde reductase (alcohol forming), acrotyl alcohol kinase, a 2-butenyl-4-phosphate kinase and a butadienesynthase (FIG. 2, steps M, D-H). In one aspect, the method includes amicrobial organism having a butadiene pathway including a glutaryl-CoAdehydrogenase, a crotyl alcohol kinase, a 2-butenyl-4-phosphate kinase,a butadiene synthase and crotonyl-CoA reductase (alcohol forming) (FIG.2, steps M, K, F, G, H). In one aspect, the method includes a microbialorganism having a butadiene pathway including a glutaryl-CoAdehydrogenase, a butadiene synthase, a crotonyl-CoA reductase (alcoholforming) and a crotyl alcohol diphosphokinase (FIG. 2, steps M, K, P,H). In one aspect, the method includes a microbial organism having abutadiene pathway including a glutaryl-CoA dehydrogenase, acrotonaldehyde reductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase, a crotonyl-CoAhydrolase, synthetase, or transferase and a crotonate reductase (FIG. 2,steps M, I, J, E, F, G, H). In one aspect, the method includes amicrobial organism having a butadiene pathway including a glutaryl-CoAdehydrogenase, a crotonaldehyde reductase (alcohol forming), a butadienesynthase, a crotonyl-CoA hydrolase, synthetase or transferase, acrotonate reductase and a crotyl alcohol diphosphokinase (FIG. 2, stepsM, I, J, E, P, H). In one aspect, the method includes a microbialorganism having a butadiene pathway including a 3-hydroxybutyryl-CoAdehydratase, a crotonyl-CoA reductase (aldehyde forming), acrotonaldehyde reductase (alcohol forming), a butadiene synthase, aglutaryl-CoA dehydrogenase and a crotyl alcohol diphosphokinase (FIG. 2,steps M, C, D, E, P, H). In one aspect, the method includes a microbialorganism having a butadiene pathway including a 3-aminobutyryl-CoAdeaminase, a crotonyl-CoA reductase (aldehyde forming), a crotonaldehydereductase (alcohol forming), a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase and a butadiene synthase (FIG. 2, steps N,D-H). In one aspect, the method includes a microbial organism having abutadiene pathway including a 3-aminobutyryl-CoA deaminase, a crotylalcohol kinase, a 2-butenyl-4-phosphate kinase, a butadiene synthase andcrotonyl-CoA reductase (alcohol forming) (FIG. 2, steps N, K, F, G, H).In one aspect, the method includes a microbial organism having abutadiene pathway including a 3-aminobutyryl-CoA deaminase, a butadienesynthase, a crotonyl-CoA reductase (alcohol forming) and a crotylalcohol diphosphokinase (FIG. 2, steps N, K, P, H). In one aspect, themethod includes a microbial organism having a butadiene pathwayincluding a 3-aminobutyryl-CoA deaminase, a crotonaldehyde reductase(alcohol forming), a crotyl alcohol kinase, a 2-butenyl-4-phosphatekinase, a butadiene synthase, a crotonyl-CoA hydrolase, synthetase, ortransferase and a crotonate reductase (FIG. 2, steps N, I, J, E, F, G,H). In one aspect, the method includes a microbial organism having abutadiene pathway including a 3-aminobutyryl-CoA deaminase, acrotonaldehyde reductase (alcohol forming), a butadiene synthase, acrotonyl-CoA hydrolase, synthetase or transferase, a crotonate reductaseand a crotyl alcohol diphosphokinase (FIG. 2, steps N, I, J, E, P, H).In one aspect, the method includes a microbial organism having abutadiene pathway including a 3-hydroxybutyryl-CoA dehydratase, acrotonyl-CoA reductase (aldehyde forming), a crotonaldehyde reductase(alcohol forming), a butadiene synthase, a 3-aminobutyryl-CoA deaminaseand a crotyl alcohol diphosphokinase (FIG. 2, steps N, C, D, E, P, H).In one aspect, the method includes a microbial organism having abutadiene pathway including a 4-hydroxybutyryl-CoA dehydratase, acrotonyl-CoA reductase (aldehyde forming), a crotonaldehyde reductase(alcohol forming), a crotyl alcohol kinase, a 2-butenyl-4-phosphatekinase and a butadiene synthase (FIG. 2, steps O, D-H). In one aspect,the method includes a microbial organism having a butadiene pathwayincluding a 4-hydroxybutyryl-CoA dehydratase, a crotyl alcohol kinase, a2-butenyl-4-phosphate kinase, a butadiene synthase and crotonyl-CoAreductase (alcohol forming) (FIG. 2, steps O, K, F, G, H). In oneaspect, the method includes a microbial organism having a butadienepathway including a 4-hydroxybutyryl-CoA dehydratase, a butadienesynthase, a crotonyl-CoA reductase (alcohol forming) and a crotylalcohol diphosphokinase (FIG. 2, steps O, K, P, H). In one aspect, themethod includes a microbial organism having a butadiene pathwayincluding a 4-hydroxybutyryl-CoA dehydratase, a crotonaldehyde reductase(alcohol forming), a crotyl alcohol kinase, a 2-butenyl-4-phosphatekinase, a butadiene synthase, a crotonyl-CoA hydrolase, synthetase, ortransferase and a crotonate reductase (FIG. 2, steps O, I, J, E, F, G,H). In one aspect, the method includes a microbial organism having abutadiene pathway including a 4-hydroxybutyryl-CoA dehydratase, acrotonaldehyde reductase (alcohol forming), a butadiene synthase, acrotonyl-CoA hydrolase, synthetase or transferase, a crotonate reductaseand a crotyl alcohol diphosphokinase (FIG. 2, steps O, I, J, E, P, H).In one aspect, the method includes a microbial organism having abutadiene pathway including a 3-hydroxybutyryl-CoA dehydratase, acrotonyl-CoA reductase (aldehyde forming), a crotonaldehyde reductase(alcohol forming), a butadiene synthase, a 4-hydroxybutyryl-CoAdehydratase and a crotyl alcohol diphosphokinase (FIG. 2, steps O, C, D,E, P, H).

In some embodiments, the invention provides a method for producingbutadiene that includes culturing a non-naturally occurring microbialorganism, including a microbial organism having a butadiene pathway, thebutadiene pathway including at least one exogenous nucleic acid encodinga butadiene pathway enzyme expressed in a sufficient amount to producebutadiene, the butadiene pathway including an erythrose-4-phosphatereductase, an erythritol-4-phospate cytidylyltransferase, a 4-(cytidine5′-diphospho)-erythritol kinase, an erythritol 2,4-cyclodiphosphatesynthase, a 1-hydroxy-2-butenyl 4-diphosphate synthase, a1-hydroxy-2-butenyl 4-diphosphate reductase, a butenyl 4-diphosphateisomerase, a butadiene synthase, an erythrose-4-phosphate kinase, anerythrose reductase or an erythritol kinase (FIG. 3). In one aspect, themethod includes a microbial organism having a butadiene pathwayincluding an erythrose-4-phosphate reductase, an erythritol-4-phospatecytidylyltransferase, a 4-(cytidine 5′-diphospho)-erythritol kinase, anerythritol 2,4-cyclodiphosphate synthase, a 1-hydroxy-2-butenyl4-diphosphate synthase, a 1-hydroxy-2-butenyl 4-diphosphate reductaseand a butadiene synthase (FIG. 3, steps A-F, and H). In one aspect, themethod includes a microbial organism having a butadiene pathwayincluding an erythrose-4-phosphate reductase, an erythritol-4-phospatecytidylyltransferase, a 4-(cytidine 5′-diphospho)-erythritol kinase, anerythritol 2,4-cyclodiphosphate synthase, a 1-hydroxy-2-butenyl4-diphosphate synthase, a 1-hydroxy-2-butenyl 4-diphosphate reductase, abutenyl 4-diphosphate isomerase and butadiene synthase (FIG. 3, stepsA-H). In one aspect, the method includes a microbial organism having abutadiene pathway including an erythritol-4-phospatecytidylyltransferase, a 4-(cytidine 5′-diphospho)-erythritol kinase, anerythritol 2,4-cyclodiphosphate synthase, a 1-hydroxy-2-butenyl4-diphosphate synthase, a 1-hydroxy-2-butenyl 4-diphosphate reductase, abutadiene synthase, an erythrose-4-phosphate kinase, an erythrosereductase and a erythritol kinase (FIG. 3, steps I, J, K, B-F, H). Inone aspect, the method includes a microbial organism having a butadienepathway including an erythritol-4-phospate cytidylyltransferase, a4-(cytidine 5′-diphospho)-erythritol kinase, an erythritol2,4-cyclodiphosphate synthase, a 1-hydroxy-2-butenyl 4-diphosphatesynthase, a 1-hydroxy-2-butenyl 4-diphosphate reductase, a butenyl4-diphosphate isomerase, a butadiene synthase, an erythrose-4-phosphatekinase, an erythrose reductase and an erythritol kinase (FIG. 3, stepsI, J, K, B-H).

In some embodiments, the invention provides a method for producingbutadiene that includes culturing a non-naturally occurring microbialorganism, including a microbial organism having a butadiene pathway, thebutadiene pathway including at least one exogenous nucleic acid encodinga butadiene pathway enzyme expressed in a sufficient amount to producebutadiene, the butadiene pathway including a malonyl-CoA:acetyl-CoAacyltransferase, a 3-oxoglutaryl-CoA reductase (ketone-reducing), a3-hydroxyglutaryl-CoA reductase (aldehyde forming), a3-hydroxy-5-oxopentanoate reductase, a 3,5-dihydroxypentanoate kinase, a3-hydroxy-5-phosphonatooxypentanoate kinase, a3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthase,a 3-hydroxyglutaryl-CoA reductase (alcohol forming), a 3-oxoglutaryl-CoAreductase (aldehyde forming), a 3,5-dioxopentanoate reductase (ketonereducing), a 3,5-dioxopentanoate reductase (aldehyde reducing), a5-hydroxy-3-oxopentanoate reductase or a 3-oxo-glutaryl-CoA reductase(CoA reducing and alcohol forming) (FIG. 4). In one aspect, the methodincludes a microbial organism having a butadiene pathway including amalonyl-CoA:acetyl-CoA acyltransferase, a 3-oxoglutaryl-CoA reductase(ketone-reducing), a 3-hydroxyglutaryl-CoA reductase (aldehyde forming),a 3-hydroxy-5-oxopentanoate reductase, a 3,5-dihydroxypentanoate kinase,a 3-hydroxy-5-phosphonatooxypentanoate kinase, a3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase and a butadienesynthase (FIG. 4, steps A-I). In one aspect, the method includes amicrobial organism having a butadiene pathway including amalonyl-CoA:acetyl-CoA acyltransferase, a 3,5-dihydroxypentanoatekinase, a 3-hydroxy-5-phosphonatooxypentanoate kinase, a3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthase,a 3-oxoglutaryl-CoA reductase (aldehyde forming), a 3,5-dioxopentanoatereductase (aldehyde reducing) and a 5-hydroxy-3-oxopentanoate reductase.(FIG. 4, steps A, K, M, N, E, F, G, H, I). In one aspect, the methodincludes a microbial organism having a butadiene pathway including amalonyl-CoA:acetyl-CoA acyltransferase, a 3-hydroxy-5-oxopentanoatereductase, a 3,5-dihydroxypentanoate kinase, a3-Hydroxy-5-phosphonatooxypentanoate kinase, a3-Hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthase,a 3-oxoglutaryl-CoA reductase (aldehyde forming) and a3,5-dioxopentanoate reductase (ketone reducing). (FIG. 4, steps A, K, L,D, E, F, G, H, I). In one aspect, the method includes a microbialorganism having a butadiene pathway including a malonyl-CoA:acetyl-CoAacyltransferase, a 3,5-dihydroxypentanoate kinase, a3-hydroxy-5-phosphonatooxypentanoate kinase, a3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthase,a 5-hydroxy-3-oxopentanoate reductase and a 3-oxo-glutaryl-CoA reductase(CoA reducing and alcohol forming). (FIG. 4, steps A, O, N, E, F, G, H,I). In one aspect, the method includes a microbial organism having abutadiene pathway including a malonyl-CoA:acetyl-CoA acyltransferase, a3-oxoglutaryl-CoA reductase (ketone-reducing), a 3,5-dihydroxypentanoatekinase, a 3-hydroxy-5-phosphonatooxypentanoate kinase, a3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoatedecarboxylase, a butenyl 4-diphosphate isomerase, a butadiene synthaseand a 3-hydroxyglutaryl-CoA reductase (alcohol forming). (FIG. 4, stepsA, B, J, E, F, G, H, I).

Suitable purification and/or assays to test for the production ofbutadiene can be performed using well known methods. Suitable replicatessuch as triplicate cultures can be grown for each engineered strain tobe tested. For example, product and byproduct formation in theengineered production host can be monitored. The final product andintermediates, and other organic compounds, can be analyzed by methodssuch as HPLC (High Performance Liquid Chromatography), GC-MS (GasChromatography-Mass Spectroscopy) and LC-MS (Liquid Chromatography-MassSpectroscopy) or other suitable analytical methods using routineprocedures well known in the art. The release of product in thefermentation broth can also be tested with the culture supernatant.Byproducts and residual glucose can be quantified by HPLC using, forexample, a refractive index detector for glucose and alcohols, and a UVdetector for organic acids (Lin et al., Biotechnol. Bioeng. 90:775-779(2005)), or other suitable assay and detection methods well known in theart. The individual enzyme or protein activities from the exogenous DNAsequences can also be assayed using methods well known in the art. Fortypical Assay Methods, see Manual on Hydrocarbon Analysis (ASTM ManulaSeries, A. W. Drews, ed., 6th edition, 1998, American Society forTesting and Materials, Baltimore, Md.

The butadiene can be separated from other components in the cultureusing a variety of methods well known in the art. Such separationmethods include, for example, extraction procedures as well as methodsthat include continuous liquid-liquid extraction, pervaporation,membrane filtration, membrane separation, reverse osmosis,electrodialysis, distillation, crystallization, centrifugation,extractive filtration, ion exchange chromatography, size exclusionchromatography, adsorption chromatography, and ultrafiltration. All ofthe above methods are well known in the art.

Any of the non-naturally occurring microbial organisms described hereincan be cultured to produce and/or secrete the biosynthetic products ofthe invention. For example, the butadiene producers can be cultured forthe biosynthetic production of butadiene.

For the production of butadiene, the recombinant strains are cultured ina medium with carbon source and other essential nutrients. It issometimes desirable and can be highly desirable to maintain anaerobicconditions in the fermenter to reduce the cost of the overall process.Such conditions can be obtained, for example, by first sparging themedium with nitrogen and then sealing the flasks with a septum andcrimp-cap. For strains where growth is not observed anaerobically,microaerobic or substantially anaerobic conditions can be applied byperforating the septum with a small hole for limited aeration. Exemplaryanaerobic conditions have been described previously and are well-knownin the art. Exemplary aerobic and anaerobic conditions are described,for example, in United State publication 2009/0047719, filed Aug. 10,2007. Fermentations can be performed in a batch, fed-batch or continuousmanner, as disclosed herein.

If desired, the pH of the medium can be maintained at a desired pH, inparticular neutral pH, such as a pH of around 7 by addition of a base,such as NaOH or other bases, or acid, as needed to maintain the culturemedium at a desirable pH. The growth rate can be determined by measuringoptical density using a spectrophotometer (600 nm), and the glucoseuptake rate by monitoring carbon source depletion over time.

The growth medium can include, for example, any carbohydrate sourcewhich can supply a source of carbon to the non-naturally occurringmicroorganism. Such sources include, for example, sugars such asglucose, xylose, arabinose, galactose, mannose, fructose, sucrose andstarch. Other sources of carbohydrate include, for example, renewablefeedstocks and biomass. Exemplary types of biomasses that can be used asfeedstocks in the methods of the invention include cellulosic biomass,hemicellulosic biomass and lignin feedstocks or portions of feedstocks.Such biomass feedstocks contain, for example, carbohydrate substratesuseful as carbon sources such as glucose, xylose, arabinose, galactose,mannose, fructose and starch. Given the teachings and guidance providedherein, those skilled in the art will understand that renewablefeedstocks and biomass other than those exemplified above also can beused for culturing the microbial organisms of the invention for theproduction of butadiene.

In addition to renewable feedstocks such as those exemplified above, thebutadiene microbial organisms of the invention also can be modified forgrowth on syngas as its source of carbon. In this specific embodiment,one or more proteins or enzymes are expressed in the butadiene producingorganisms to provide a metabolic pathway for utilization of syngas orother gaseous carbon source.

Synthesis gas, also known as syngas or producer gas, is the majorproduct of gasification of coal and of carbonaceous materials such asbiomass materials, including agricultural crops and residues. Syngas isa mixture primarily of H₂ and CO and can be obtained from thegasification of any organic feedstock, including but not limited tocoal, coal oil, natural gas, biomass, and waste organic matter.Gasification is generally carried out under a high fuel to oxygen ratio.Although largely H₂ and CO, syngas can also include CO₂ and other gasesin smaller quantities. Thus, synthesis gas provides a cost effectivesource of gaseous carbon such as CO and, additionally, CO₂.

The Wood-Ljungdahl pathway catalyzes the conversion of CO and H₂ toacetyl-CoA and other products such as acetate. Organisms capable ofutilizing CO and syngas also generally have the capability of utilizingCO₂ and CO₂/H₂ mixtures through the same basic set of enzymes andtransformations encompassed by the Wood-Ljungdahl pathway. H₂-dependentconversion of CO₂ to acetate by microorganisms was recognized longbefore it was revealed that CO also could be used by the same organismsand that the same pathways were involved. Many acetogens have been shownto grow in the presence of CO₂ and produce compounds such as acetate aslong as hydrogen is present to supply the necessary reducing equivalents(see for example, Drake, Acetogenesis, pp. 3-60 Chapman and Hall, NewYork, (1994)). This can be summarized by the following equation:

2CO₂+4H₂ +nADP+nPi→CH₃COOH+2H₂O+nATP

Hence, non-naturally occurring microorganisms possessing theWood-Ljungdahl pathway can utilize CO₂ and H₂ mixtures as well for theproduction of acetyl-CoA and other desired products.

The Wood-Ljungdahl pathway is well known in the art and consists of 12reactions which can be separated into two branches: (1) methyl branchand (2) carbonyl branch. The methyl branch converts syngas tomethyl-tetrahydrofolate (methyl-THF) whereas the carbonyl branchconverts methyl-THF to acetyl-CoA. The reactions in the methyl branchare catalyzed in order by the following enzymes or proteins: ferredoxinoxidoreductase, formate dehydrogenase, formyltetrahydrofolatesynthetase, methenyltetrahydrofolate cyclodehydratase,methylenetetrahydrofolate dehydrogenase and methylenetetrahydrofolatereductase. The reactions in the carbonyl branch are catalyzed in orderby the following enzymes or proteins: methyltetrahydrofolate:corrinoidprotein methyltransferase (for example, AcsE), corrinoid iron-sulfurprotein, nickel-protein assembly protein (for example, AcsF),ferredoxin, acetyl-CoA synthase, carbon monoxide dehydrogenase andnickel-protein assembly protein (for example, CooC). Following theteachings and guidance provided herein for introducing a sufficientnumber of encoding nucleic acids to generate a butadiene pathway, thoseskilled in the art will understand that the same engineering design alsocan be performed with respect to introducing at least the nucleic acidsencoding the Wood-Ljungdahl enzymes or proteins absent in the hostorganism. Therefore, introduction of one or more encoding nucleic acidsinto the microbial organisms of the invention such that the modifiedorganism contains the complete Wood-Ljungdahl pathway will confer syngasutilization ability.

Additionally, the reductive (reverse) tricarboxylic acid cycle coupledwith carbon monoxide dehydrogenase and/or hydrogenase activities canalso be used for the conversion of CO, CO₂ and/or H₂ to acetyl-CoA andother products such as acetate. Organisms capable of fixing carbon viathe reductive TCA pathway can utilize one or more of the followingenzymes: ATP citrate-lyase, citrate lyase, aconitase, isocitratedehydrogenase, alpha-ketoglutarate:ferredoxin oxidoreductase,succinyl-CoA synthetase, succinyl-CoA transferase, fumarate reductase,fumarase, malate dehydrogenase, NAD(P)H:ferredoxin oxidoreductase,carbon monoxide dehydrogenase, and hydrogenase. Specifically, thereducing equivalents extracted from CO and/or H₂ by carbon monoxidedehydrogenase and hydrogenase are utilized to fix CO₂ via the reductiveTCA cycle into acetyl-CoA or acetate. Acetate can be converted toacetyl-CoA by enzymes such as acetyl-CoA transferase, acetatekinase/phosphotransacetylase, and acetyl-CoA synthetase. Acetyl-CoA canbe converted to the butadiene, glyceraldehyde-3-phosphate,phosphoenolpyruvate, and pyruvate, by pyruvate:ferredoxin oxidoreductaseand the enzymes of gluconeogenesis. Following the teachings and guidanceprovided herein for introducing a sufficient number of encoding nucleicacids to generate a butadiene pathway, those skilled in the art willunderstand that the same engineering design also can be performed withrespect to introducing at least the nucleic acids encoding the reductiveTCA pathway enzymes or proteins absent in the host organism. Therefore,introduction of one or more encoding nucleic acids into the microbialorganisms of the invention such that the modified organism contains thecomplete reductive TCA pathway will confer syngas utilization ability.

Accordingly, given the teachings and guidance provided herein, thoseskilled in the art will understand that a non-naturally occurringmicrobial organism can be produced that secretes the biosynthesizedcompounds of the invention when grown on a carbon source such as acarbohydrate. Such compounds include, for example, butadiene and any ofthe intermediate metabolites in the butadiene pathway. All that isrequired is to engineer in one or more of the required enzyme or proteinactivities to achieve biosynthesis of the desired compound orintermediate including, for example, inclusion of some or all of thebutadiene biosynthetic pathways. Accordingly, the invention provides anon-naturally occurring microbial organism that produces and/or secretesbutadiene when grown on a carbohydrate or other carbon source andproduces and/or secretes any of the intermediate metabolites shown inthe butadiene pathway when grown on a carbohydrate or other carbonsource. The butadiene producing microbial organisms of the invention caninitiate synthesis from an intermediate, for example, acetoacetyl-CoA,3-hydroxybutyryl-CoA, crotonyl-CoA, crotonaldehyde, crotyl alcohol,2-betenyl-phosphate, 2-butenyl-4-diphosphate, erythritol-4-phosphate,4-(cytidine 5′-diphospho)-erythritol, 2-phospho-4-(cytidine5′-diphospho)-erythritol, erythritol-2,4-cyclodiphosphate,1-hydroxy-2-butenyl 4-diphosphate, butenyl 4-diphosphate, 2-butenyl4-diphosphate, 3-oxoglutaryl-CoA, 3-hydroxyglutaryl-CoA,3-hydroxy-5-oxopentanoate, 3,5-dihydroxy pentanoate,3-hydroxy-5-phosphonatooxypentanoate,3-hydroxy-5-[hydroxy(phosphonooxy)phosphoryl]oxy pentanoate, crotonate,erythrose, erythritol, 3,5-dioxopentanoate or 5-hydroxy-3-oxopentanoate.

The non-naturally occurring microbial organisms of the invention areconstructed using methods well known in the art as exemplified herein toexogenously express at least one nucleic acid encoding a butadienepathway enzyme or protein in sufficient amounts to produce butadiene. Itis understood that the microbial organisms of the invention are culturedunder conditions sufficient to produce butadiene. Following theteachings and guidance provided herein, the non-naturally occurringmicrobial organisms of the invention can achieve biosynthesis ofbutadiene resulting in intracellular concentrations between about0.001-2000 mM or more. Generally, the intracellular concentration ofbutadiene is between about 3-1500 mM, particularly between about 5-1250mM and more particularly between about 8-1000 mM, including about 10 mM,100 mM, 200 mM, 500 mM, 800 mM, or more. Intracellular concentrationsbetween and above each of these exemplary ranges also can be achievedfrom the non-naturally occurring microbial organisms of the invention.

In some embodiments, culture conditions include anaerobic orsubstantially anaerobic growth or maintenance conditions. Exemplaryanaerobic conditions have been described previously and are well knownin the art. Exemplary anaerobic conditions for fermentation processesare described herein and are described, for example, in U.S. publication2009/0047719, filed Aug. 10, 2007. Any of these conditions can beemployed with the non-naturally occurring microbial organisms as well asother anaerobic conditions well known in the art. Under such anaerobicor substantially anaerobic conditions, the butadiene producers cansynthesize butadiene at intracellular concentrations of 5-10 mM or moreas well as all other concentrations exemplified herein. It is understoodthat, even though the above description refers to intracellularconcentrations, butadiene producing microbial organisms can producebutadiene intracellularly and/or secrete the product into the culturemedium.

In some embodiments, the carbon feedstock and other cellular uptakesources such as phosphate, ammonia, sulfate, chloride and other halogenscan be chosen to alter the isotopic distribution of the atoms present inbutadiene or any butadiene pathway intermediate. The various carbonfeedstock and other uptake sources enumerated above will be referred toherein, collectively, as “uptake sources.” Uptake sources can provideisotopic enrichment for any atom present in the product butadiene orbutadiene pathway intermediate including any butadiene impuritiesgenerated in diverging away from the pathway at any point. Isotopicenrichment can be achieved for any target atom including, for example,carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, chloride orother halogens.

In some embodiments, the uptake sources can be selected to alter thecarbon-12, carbon-13, and carbon-14 ratios. In some embodiments, theuptake sources can be selected to alter the oxygen-16, oxygen-17, andoxygen-18 ratios. In some embodiments, the uptake sources can beselected to alter the hydrogen, deuterium, and tritium ratios. In someembodiments, the uptake sources can be selected to alter the nitrogen-14and nitrogen-15 ratios. In some embodiments, the uptake sources can beselected to alter the sulfur-32, sulfur-33, sulfur-34, and sulfur-35ratios. In some embodiments, the uptake sources can be selected to alterthe phosphorus-31, phosphorus-32, and phosphorus-33 ratios. In someembodiments, the uptake sources can be selected to alter thechlorine-35, chlorine-36, and chlorine-37 ratios.

In some embodiments, a target isotopic ratio of an uptake source can beobtained via synthetic chemical enrichment of the uptake source. Suchisotopically enriched uptake sources can be purchased commercially orprepared in the laboratory. In some embodiments, a target isotopic ratioof an uptake source can be obtained by choice of origin of the uptakesource in nature. In some such embodiments, a source of carbon, forexample, can be selected from a fossil fuel-derived carbon source, whichcan be relatively depleted of carbon-14, or an environmental carbonsource, such as CO₂, which can possess a larger amount of carbon-14 thanits petroleum-derived counterpart.

The unstable carbon isotope carbon-14 or radiocarbon makes up forroughly 1 in 10¹² carbon atoms in earth's atmosphere. Carbon-14 has ahalf-life of about 5700 years. The stock is replenished in the upperatmosphere by a nuclear reaction involving cosmic rays and ordinarynitrogen (¹⁴N). Fossil fuels contain no carbon-14, as it decayed longago. Burning fossil fuels should lower the atmospheric carbon-14fraction (the ‘Suess effect’). Indeed, atmospheric carbon-14, measuredon tree rings, dropped by 2 to 2.5% from about 1850 to 1954, whennuclear bomb tests started to inject carbon-14 into the atmosphere.

ASTM D6866 was developed in the United States as a standardizedanalytical method for determining the biobased content of solid, liquid,and gaseous samples using radiocarbon dating. Specifically, ASTM D6866was developed at the request of the United States Department ofAgriculture to satisfy legislation requiring federal agencies to givepreference in procurement to manufacturers using the greatest amount ofbiomass in their products (per the Farm Security and Rural InvestmentAct of 2002). It was quickly established that radiocarbon dating was theonly viable and accurate technique to use for the determination of aproduct's biobased content. A working standard of radiocarbon dating forindustrial use was completed in 2004 and is now cited in US Federal Law(7 CFR part 2902). ASTM D6866 was first published in 2004. There havebeen several versions released since then. The current active version ofthe standard is ASTM D6866-11 effective Apr. 1, 2011.

Isotopic enrichment is readily assessed by mass spectrometry usingtechniques known in the art such as Stable Isotope Ratio MassSpectrometry (SIRMS) and Site-Specific Natural Isotopic Fractionation byNuclear Magnetic Resonance (SNIF-NMR). Such mass spectral techniques canbe integrated with separation techniques such as liquid chromatography(LC) and/or high performance liquid chromatography (HPLC).

The biobased content of monomers (i.e., Fm or fraction modern) isestimated by the ratio of carbon-14 (¹⁴C) to carbon-12 (¹²C) measured byaccelerator mass spectrometry (AMS). Specifically, the Fraction Modern(Fm) is computed from the expression: Fm=(S−B)/(M−B), where B, S and Mrepresent the ¹⁴C/¹²C ratios of the blank, the sample and the modernreference, respectively. Fraction Modern is a measurement of thedeviation of the ¹⁴C/¹²C ratio of a sample from “Modern.” Modern isdefined as 95% of the radiocarbon concentration (in AD 1950) of NBSOxalic Acid I (i.e., SRM 4990b) normalized to δ¹³C_(VPDB)=−19 per mil.Olsson, The use of Oxalic acid as a Standard. In, Radiocarbon Variationsand Absolute Chronology, Nobel Symposium, 12th Proc., John Wiley & Sons,New York (1970). AMS results are calculated using the internationallyagreed upon definition of 0.95 times the specific activity of NBS OxalicAcid I (SRM 4990b) normalized to δ¹³C_(VPDB)=−19 per mil. This isequivalent to an absolute (AD 1950) ¹⁴C/¹²C ratio of 1.176±0.010×10⁻¹².Karlen et al., Arkiv Geofysik, 4:465-471 (1968).

An oxalic acid standard (SRM 4990b or HOx 1) was made from a crop of1955 sugar beet. Although there were 1000 lbs made, this oxalic acidstandard is no longer commercially available. Another standard, OxalicAcid II, was prepared when stocks of SRM 4990b began to dwindle. TheOxalic Acid II standard (HOx 2; N.I.S.T designation SRM 4990 C) was madefrom a crop of 1977 French beet molasses. In the early 1980's, a groupof 12 laboratories measured the ratios of the two standards. The ratioof the activity of Oxalic acid II to 1 is 1.2933±0.001 (the weightedmean). Mann, Radiocarbon, 25(2):519-527 (1983). The isotopic ratio ofHOx II is −17.8 per mille. ASTM D6866-11 suggests use of SRM 4990 C forthe modern standard. A Fm=0% represents the entire lack of carbon-14atoms in a material thus indicating a fossil (for example, petroleumbased) carbon source. A Fm=100%, after correction for the post-1950 bombinjection of carbon-14 into the atmosphere, likewise indicates anentirely modern carbon source.

As described in ASTM D6866, the percent modern carbon (pMC) can begreater than 100% because of the continuing but diminishing effects ofthe 1950s nuclear testing programs, which resulted in a considerableenrichment of carbon-14 in the atmosphere as described in ASTM D6866-11.Because all sample carbon-14 activities are referenced to a “pre-bomb”standard, and because nearly all new biobased products are produced in apost-bomb environment, all pMC values (after correction for isotopicfraction) must be multiplied by 0.95 (as of 2010) to better reflect thetrue biobased content of the sample. A biobased content that is greaterthan 103% suggests that either an analytical error has occurred, or thatthe source of biobased carbon is more than several years old.

ASTM D6866 quantifies the biobased content relative to the material'stotal organic content and does not consider the inorganic carbon andother non-carbon containing substances present. To illustrate, below aresome exemplary formulations and their corresponding ASTM D6866 results:

-   -   Product 1—liquid with 50% starch-based material and 50% water.        Biobased Content=100% (product 1 has 50% organic content and        100% of that fraction is biobased);    -   Product 2—liquid with 50% starch-based material, 25%        petroleum-based, 25% water. Biobased Content=66.7% (product 2        has 75% organic content but only 50% of that fraction is        biobased);    -   Product 3—solid that is 50% glass and 50% polyethylene from        petroleum. Biobased Content=0% (product 3 has 50% organic carbon        but from fossil sources; glass is not carbon-containing);    -   Product 4—solid that is 50% glass and 50% polyethylene from        biomass. Biobased Content=100% (product 4 has 50% organic carbon        and 100% of it is renewable); and    -   Product 5—liquid with 50% soy-based material, 30%        petroleum-based, 10% water, and 10% inorganic substances.        Biobased Content=62.5% (product 5 has 80% organic carbon but        only 50% of it is renewable).

Applications of carbon-14 dating techniques to quantify bio-basedcontent of renewable materials are known in the art. Currie et al.,Nuclear Instruments and Methods in Physics Research B, 172:281-287(2000). For example, carbon-14 dating has been used to quantifybio-based content in terephthalate-containing materials. Colonna et al.,Green Chemistry, 13:2543-2548 (2011). Notably, polypropyleneterephthalate (PPT) polymers derived from renewable 1,3-propanediol andpetroleum-derived terephthalic acid resulted in Fm values near 30%(i.e., since 3/11 of the polymeric carbon derives from renewable1,3-propanediol and 8/11 from the fossil end member terephthalic acid).Currie et al., supra. In contrast, polybutylene terephthalate polymerderived from both renewable 1,4-butanediol and renewable terephthalicacid resulted in bio-based content exceeding 90%. Colonna et al., supra.

Accordingly, in some embodiments, the present invention providesbutadiene or a butadiene intermediate that has a carbon-12, carbon-13,and carbon-14 ratio that reflects an atmospheric carbon uptake source.For example, in some aspects the butadiene or a butadiene intermediatecan have an Fm value of at least 60%, at least 65%, at least 70%, atleast 75%, at least 80%, at least 85%, at least 90%, at least 95%, atleast 98 or at much as 100%. In some such embodiments, the uptake sourceis CO₂. In some embodiments, the present invention provides butadiene ora butadiene intermediate that has a carbon-12, carbon-13, and carbon-14ratio that reflects petroleum-based carbon uptake source. In thisaspect, the butadiene or a butadiene intermediate can have an Fm valueof less than 10%, less than 5%, less than 2% or less than 1%. In someembodiments, the present invention provides butadiene or a butadieneintermediate that has a carbon-12, carbon-13, and carbon-14 ratio thatis obtained by a combination of an atmospheric carbon uptake source witha petroleum-based uptake source. Such combination of uptake sources isone means by which the carbon-12, carbon-13, and carbon-14 ratio can bevaried.

In addition to the culturing and fermentation conditions disclosedherein, growth condition for achieving biosynthesis of butadiene caninclude the addition of an osmoprotectant to the culturing conditions.In certain embodiments, the non-naturally occurring microbial organismsof the invention can be sustained, cultured or fermented as describedherein in the presence of an osmoprotectant. Briefly, an osmoprotectantrefers to a compound that acts as an osmolyte and helps a microbialorganism as described herein survive osmotic stress. Osmoprotectantsinclude, but are not limited to, betaines, amino acids, and the sugartrehalose. Non-limiting examples of such are glycine betaine, pralinebetaine, dimethylthetin, dimethylslfonioproprionate,3-dimethylsulfonio-2-methylproprionate, pipecolic acid,dimethylsulfonioacetate, choline, L-carnitine and ectoine. In oneaspect, the osmoprotectant is glycine betaine. It is understood to oneof ordinary skill in the art that the amount and type of osmoprotectantsuitable for protecting a microbial organism described herein fromosmotic stress will depend on the microbial organism used. The amount ofosmoprotectant in the culturing conditions can be, for example, no morethan about 0.1 mM, no more than about 0.5 mM, no more than about 1.0 mM,no more than about 1.5 mM, no more than about 2.0 mM, no more than about2.5 mM, no more than about 3.0 mM, no more than about 5.0 mM, no morethan about 7.0 mM, no more than about 10 mM, no more than about 50 mM,no more than about 100 mM or no more than about 500 mM.

The culture conditions can include, for example, liquid cultureprocedures as well as fermentation and other large scale cultureprocedures. As described herein, particularly useful yields of thebiosynthetic products of the invention can be obtained under anaerobicor substantially anaerobic culture conditions.

As described herein, one exemplary growth condition for achievingbiosynthesis of butadiene includes anaerobic culture or fermentationconditions. In certain embodiments, the non-naturally occurringmicrobial organisms of the invention can be sustained, cultured orfermented under anaerobic or substantially anaerobic conditions.Briefly, anaerobic conditions refers to an environment devoid of oxygen.Substantially anaerobic conditions include, for example, a culture,batch fermentation or continuous fermentation such that the dissolvedoxygen concentration in the medium remains between 0 and 10% ofsaturation. Substantially anaerobic conditions also includes growing orresting cells in liquid medium or on solid agar inside a sealed chambermaintained with an atmosphere of less than 1% oxygen. The percent ofoxygen can be maintained by, for example, sparging the culture with anN₂/CO₂ mixture or other suitable non-oxygen gas or gases.

The culture conditions described herein can be scaled up and growncontinuously for manufacturing of butadiene. Exemplary growth proceduresinclude, for example, fed-batch fermentation and batch separation;fed-batch fermentation and continuous separation, or continuousfermentation and continuous separation. All of these processes are wellknown in the art. Fermentation procedures are particularly useful forthe biosynthetic production of commercial quantities of butadiene.Generally, and as with non-continuous culture procedures, the continuousand/or near-continuous production of butadiene will include culturing anon-naturally occurring butadiene producing organism of the invention insufficient nutrients and medium to sustain and/or nearly sustain growthin an exponential phase. Continuous culture under such conditions can beinclude, for example, growth for 1 day, 2, 3, 4, 5, 6 or 7 days or more.Additionally, continuous culture can include longer time periods of 1week, 2, 3, 4 or 5 or more weeks and up to several months.Alternatively, organisms of the invention can be cultured for hours, ifsuitable for a particular application. It is to be understood that thecontinuous and/or near-continuous culture conditions also can includeall time intervals in between these exemplary periods. It is furtherunderstood that the time of culturing the microbial organism of theinvention is for a sufficient period of time to produce a sufficientamount of product for a desired purpose.

Fermentation procedures are well known in the art. Briefly, fermentationfor the biosynthetic production of butadiene can be utilized in, forexample, fed-batch fermentation and batch separation; fed-batchfermentation and continuous separation, or continuous fermentation andcontinuous separation. Examples of batch and continuous fermentationprocedures are well known in the art.

In addition to the above fermentation procedures using the butadieneproducers of the invention for continuous production of substantialquantities of butadiene, the butadiene producers also can be, forexample, simultaneously subjected to chemical synthesis procedures toconvert the product to other compounds or the product can be separatedfrom the fermentation culture and sequentially subjected to chemical orenzymatic conversion to convert the product to other compounds, ifdesired.

To generate better producers, metabolic modeling can be utilized tooptimize growth conditions. Modeling can also be used to design geneknockouts that additionally optimize utilization of the pathway (see,for example, U.S. patent publications US 2002/0012939, US 2003/0224363,US 2004/0029149, US 2004/0072723, US 2003/0059792, US 2002/0168654 andUS 2004/0009466, and U.S. Pat. No. 7,127,379). Modeling analysis allowsreliable predictions of the effects on cell growth of shifting themetabolism towards more efficient production of butadiene.

One computational method for identifying and designing metabolicalterations favoring biosynthesis of a desired product is the OptKnockcomputational framework (Burgard et al., Biotechnol. Bioeng. 84:647-657(2003)). OptKnock is a metabolic modeling and simulation program thatsuggests gene deletion or disruption strategies that result ingenetically stable microorganisms which overproduce the target product.Specifically, the framework examines the complete metabolic and/orbiochemical network of a microorganism in order to suggest geneticmanipulations that force the desired biochemical to become an obligatorybyproduct of cell growth. By coupling biochemical production with cellgrowth through strategically placed gene deletions or other functionalgene disruption, the growth selection pressures imposed on theengineered strains after long periods of time in a bioreactor lead toimprovements in performance as a result of the compulsory growth-coupledbiochemical production. Lastly, when gene deletions are constructedthere is a negligible possibility of the designed strains reverting totheir wild-type states because the genes selected by OptKnock are to becompletely removed from the genome. Therefore, this computationalmethodology can be used to either identify alternative pathways thatlead to biosynthesis of a desired product or used in connection with thenon-naturally occurring microbial organisms for further optimization ofbiosynthesis of a desired product.

Briefly, OptKnock is a term used herein to refer to a computationalmethod and system for modeling cellular metabolism. The OptKnock programrelates to a framework of models and methods that incorporate particularconstraints into flux balance analysis (FBA) models. These constraintsinclude, for example, qualitative kinetic information, qualitativeregulatory information, and/or DNA microarray experimental data.OptKnock also computes solutions to various metabolic problems by, forexample, tightening the flux boundaries derived through flux balancemodels and subsequently probing the performance limits of metabolicnetworks in the presence of gene additions or deletions. OptKnockcomputational framework allows the construction of model formulationsthat allow an effective query of the performance limits of metabolicnetworks and provides methods for solving the resulting mixed-integerlinear programming problems. The metabolic modeling and simulationmethods referred to herein as OptKnock are described in, for example,U.S. publication 2002/0168654, filed Jan. 10, 2002, in InternationalPatent No. PCT/US02/00660, filed Jan. 10, 2002, and U.S. publication2009/0047719, filed Aug. 10, 2007.

Another computational method for identifying and designing metabolicalterations favoring biosynthetic production of a product is a metabolicmodeling and simulation system termed SimPheny®. This computationalmethod and system is described in, for example, U.S. publication2003/0233218, filed Jun. 14, 2002, and in International PatentApplication No. PCT/US03/18838, filed Jun. 13, 2003. SimPheny® is acomputational system that can be used to produce a network model insilico and to simulate the flux of mass, energy or charge through thechemical reactions of a biological system to define a solution spacethat contains any and all possible functionalities of the chemicalreactions in the system, thereby determining a range of allowedactivities for the biological system. This approach is referred to asconstraints-based modeling because the solution space is defined byconstraints such as the known stoichiometry of the included reactions aswell as reaction thermodynamic and capacity constraints associated withmaximum fluxes through reactions. The space defined by these constraintscan be interrogated to determine the phenotypic capabilities andbehavior of the biological system or of its biochemical components.

These computational approaches are consistent with biological realitiesbecause biological systems are flexible and can reach the same result inmany different ways. Biological systems are designed throughevolutionary mechanisms that have been restricted by fundamentalconstraints that all living systems must face. Therefore,constraints-based modeling strategy embraces these general realities.Further, the ability to continuously impose further restrictions on anetwork model via the tightening of constraints results in a reductionin the size of the solution space, thereby enhancing the precision withwhich physiological performance or phenotype can be predicted.

Given the teachings and guidance provided herein, those skilled in theart will be able to apply various computational frameworks for metabolicmodeling and simulation to design and implement biosynthesis of adesired compound in host microbial organisms. Such metabolic modelingand simulation methods include, for example, the computational systemsexemplified above as SimPheny® and OptKnock. For illustration of theinvention, some methods are described herein with reference to theOptKnock computation framework for modeling and simulation. Thoseskilled in the art will know how to apply the identification, design andimplementation of the metabolic alterations using OptKnock to any ofsuch other metabolic modeling and simulation computational frameworksand methods well known in the art.

The methods described above will provide one set of metabolic reactionsto disrupt. Elimination of each reaction within the set or metabolicmodification can result in a desired product as an obligatory productduring the growth phase of the organism. Because the reactions areknown, a solution to the bilevel OptKnock problem also will provide theassociated gene or genes encoding one or more enzymes that catalyze eachreaction within the set of reactions. Identification of a set ofreactions and their corresponding genes encoding the enzymesparticipating in each reaction is generally an automated process,accomplished through correlation of the reactions with a reactiondatabase having a relationship between enzymes and encoding genes.

Once identified, the set of reactions that are to be disrupted in orderto achieve production of a desired product are implemented in the targetcell or organism by functional disruption of at least one gene encodingeach metabolic reaction within the set. One particularly useful means toachieve functional disruption of the reaction set is by deletion of eachencoding gene. However, in some instances, it can be beneficial todisrupt the reaction by other genetic aberrations including, forexample, mutation, deletion of regulatory regions such as promoters orcis binding sites for regulatory factors, or by truncation of the codingsequence at any of a number of locations. These latter aberrations,resulting in less than total deletion of the gene set can be useful, forexample, when rapid assessments of the coupling of a product are desiredor when genetic reversion is less likely to occur.

To identify additional productive solutions to the above describedbilevel OptKnock problem which lead to further sets of reactions todisrupt or metabolic modifications that can result in the biosynthesis,including growth-coupled biosynthesis of a desired product, anoptimization method, termed integer cuts, can be implemented. Thismethod proceeds by iteratively solving the OptKnock problem exemplifiedabove with the incorporation of an additional constraint referred to asan integer cut at each iteration. Integer cut constraints effectivelyprevent the solution procedure from choosing the exact same set ofreactions identified in any previous iteration that obligatorily couplesproduct biosynthesis to growth. For example, if a previously identifiedgrowth-coupled metabolic modification specifies reactions 1, 2, and 3for disruption, then the following constraint prevents the samereactions from being simultaneously considered in subsequent solutions.The integer cut method is well known in the art and can be founddescribed in, for example, Burgard et al., Biotechnol. Prog. 17:791-797(2001). As with all methods described herein with reference to their usein combination with the OptKnock computational framework for metabolicmodeling and simulation, the integer cut method of reducing redundancyin iterative computational analysis also can be applied with othercomputational frameworks well known in the art including, for example,SimPheny®.

The methods exemplified herein allow the construction of cells andorganisms that biosynthetically produce a desired product, including theobligatory coupling of production of a target biochemical product togrowth of the cell or organism engineered to harbor the identifiedgenetic alterations. Therefore, the computational methods describedherein allow the identification and implementation of metabolicmodifications that are identified by an in silico method selected fromOptKnock or SimPheny®. The set of metabolic modifications can include,for example, addition of one or more biosynthetic pathway enzymes and/orfunctional disruption of one or more metabolic reactions including, forexample, disruption by gene deletion.

As discussed above, the OptKnock methodology was developed on thepremise that mutant microbial networks can be evolved towards theircomputationally predicted maximum-growth phenotypes when subjected tolong periods of growth selection. In other words, the approach leveragesan organism's ability to self-optimize under selective pressures. TheOptKnock framework allows for the exhaustive enumeration of genedeletion combinations that force a coupling between biochemicalproduction and cell growth based on network stoichiometry. Theidentification of optimal gene/reaction knockouts requires the solutionof a bilevel optimization problem that chooses the set of activereactions such that an optimal growth solution for the resulting networkoverproduces the biochemical of interest (Burgard et al., Biotechnol.Bioeng. 84:647-657 (2003)).

An in silico stoichiometric model of E. coli metabolism can be employedto identify essential genes for metabolic pathways as exemplifiedpreviously and described in, for example, U.S. patent publications US2002/0012939, US 2003/0224363, US 2004/0029149, US 2004/0072723, US2003/0059792, US 2002/0168654 and US 2004/0009466, and in U.S. Pat. No.7,127,379. As disclosed herein, the OptKnock mathematical framework canbe applied to pinpoint gene deletions leading to the growth-coupledproduction of a desired product. Further, the solution of the bilevelOptKnock problem provides only one set of deletions. To enumerate allmeaningful solutions, that is, all sets of knockouts leading togrowth-coupled production formation, an optimization technique, termedinteger cuts, can be implemented. This entails iteratively solving theOptKnock problem with the incorporation of an additional constraintreferred to as an integer cut at each iteration, as discussed above.

As disclosed herein, a nucleic acid encoding a desired activity of abutadiene pathway can be introduced into a host organism. In some cases,it can be desirable to modify an activity of a butadiene pathway enzymeor protein to increase production of butadiene. For example, knownmutations that increase the activity of a protein or enzyme can beintroduced into an encoding nucleic acid molecule. Additionally,optimization methods can be applied to increase the activity of anenzyme or protein and/or decrease an inhibitory activity, for example,decrease the activity of a negative regulator.

One such optimization method is directed evolution. Directed evolutionis a powerful approach that involves the introduction of mutationstargeted to a specific gene in order to improve and/or alter theproperties of an enzyme. Improved and/or altered enzymes can beidentified through the development and implementation of sensitivehigh-throughput screening assays that allow the automated screening ofmany enzyme variants (for example, >10⁴). Iterative rounds ofmutagenesis and screening typically are performed to afford an enzymewith optimized properties. Computational algorithms that can help toidentify areas of the gene for mutagenesis also have been developed andcan significantly reduce the number of enzyme variants that need to begenerated and screened. Numerous directed evolution technologies havebeen developed (for reviews, see Hibbert et al., Biomol. Eng 22:11-19(2005); Huisman and Lalonde, In Biocatalysis in the pharmaceutical andbiotechnology industries pgs. 717-742 (2007), Patel (ed.), CRC Press;Otten and Quax. Biomol. Eng 22:1-9 (2005).; and Sen et al., ApplBiochem. Biotechnol 143:212-223 (2007)) to be effective at creatingdiverse variant libraries, and these methods have been successfullyapplied to the improvement of a wide range of properties across manyenzyme classes. Enzyme characteristics that have been improved and/oraltered by directed evolution technologies include, for example:selectivity/specificity, for conversion of non-natural substrates;temperature stability, for robust high temperature processing; pHstability, for bioprocessing under lower or higher pH conditions;substrate or product tolerance, so that high product titers can beachieved; binding (K_(m)), including broadening substrate binding toinclude non-natural substrates; inhibition (K_(i)), to remove inhibitionby products, substrates, or key intermediates; activity (kcat), toincreases enzymatic reaction rates to achieve desired flux; expressionlevels, to increase protein yields and overall pathway flux; oxygenstability, for operation of air sensitive enzymes under aerobicconditions; and anaerobic activity, for operation of an aerobic enzymein the absence of oxygen.

Described below in more detail are exemplary methods that have beendeveloped for the mutagenesis and diversification of genes to targetdesired properties of specific enzymes. Such methods are well known tothose skilled in the art. Any of these can be used to alter and/oroptimize the activity of a butadiene pathway enzyme or protein.

EpPCR (Pritchard et al., J. Theor. Biol. 234:497-509 (2005)) introducesrandom point mutations by reducing the fidelity of DNA polymerase in PCRreactions by the addition of Mn²⁺ ions, by biasing dNTP concentrations,or by other conditional variations. The five step cloning process toconfine the mutagenesis to the target gene of interest involves: 1)error-prone PCR amplification of the gene of interest; 2) restrictionenzyme digestion; 3) gel purification of the desired DNA fragment; 4)ligation into a vector; 5) transformation of the gene variants into asuitable host and screening of the library for improved performance.This method can generate multiple mutations in a single genesimultaneously, which can be useful to screen a larger number ofpotential variants having a desired activity. A high number of mutantscan be generated by EpPCR, so a high-throughput screening assay or aselection method, for example, using robotics, is useful to identifythose with desirable characteristics.

Error-prone Rolling Circle Amplification (epRCA) (Fujii et al., NucleicAcids Res. 32:e145 (2004); and Fujii et al., Nat. Protoc. 1:2493-2497(2006)) has many of the same elements as epPCR except a whole circularplasmid is used as the template and random 6-mers with exonucleaseresistant thiophosphate linkages on the last 2 nucleotides are used toamplify the plasmid followed by transformation into cells in which theplasmid is re-circularized at tandem repeats. Adjusting the Mn²⁺concentration can vary the mutation rate somewhat. This technique uses asimple error-prone, single-step method to create a full copy of theplasmid with 3-4 mutations/kbp. No restriction enzyme digestion orspecific primers are required. Additionally, this method is typicallyavailable as a commercially available kit.

DNA or Family Shuffling (Stemmer, Proc Natl Acad Sci USA 91:10747-10751(1994)); and Stemmer, Nature 370:389-391 (1994)) typically involvesdigestion of two or more variant genes with nucleases such as Dnase I orEndoV to generate a pool of random fragments that are reassembled bycycles of annealing and extension in the presence of DNA polymerase tocreate a library of chimeric genes. Fragments prime each other andrecombination occurs when one copy primes another copy (templateswitch). This method can be used with >1 kbp DNA sequences. In additionto mutational recombinants created by fragment reassembly, this methodintroduces point mutations in the extension steps at a rate similar toerror-prone PCR. The method can be used to remove deleterious, randomand neutral mutations.

Staggered Extension (StEP) (Zhao et al., Nat. Biotechnol. 16:258-261(1998)) entails template priming followed by repeated cycles of 2 stepPCR with denaturation and very short duration of annealing/extension (asshort as 5 sec). Growing fragments anneal to different templates andextend further, which is repeated until full-length sequences are made.Template switching means most resulting fragments have multiple parents.Combinations of low-fidelity polymerases (Taq and Mutazyme) reduceerror-prone biases because of opposite mutational spectra.

In Random Priming Recombination (RPR) random sequence primers are usedto generate many short DNA fragments complementary to different segmentsof the template (Shao et al., Nucleic Acids Res 26:681-683 (1998)). Basemisincorporation and mispriming via epPCR give point mutations. ShortDNA fragments prime one another based on homology and are recombined andreassembled into full-length by repeated thermocycling. Removal oftemplates prior to this step assures low parental recombinants. Thismethod, like most others, can be performed over multiple iterations toevolve distinct properties. This technology avoids sequence bias, isindependent of gene length, and requires very little parent DNA for theapplication.

In Heteroduplex Recombination linearized plasmid DNA is used to formheteroduplexes that are repaired by mismatch repair (Volkov et al,Nucleic Acids Res. 27:e18 (1999); and Volkov et al., Methods Enzymol.328:456-463 (2000)). The mismatch repair step is at least somewhatmutagenic. Heteroduplexes transform more efficiently than linearhomoduplexes. This method is suitable for large genes and whole operons.

Random Chimeragenesis on Transient Templates (RACHITT) (Coco et al.,Nat. Biotechnol. 19:354-359 (2001)) employs Dnase I fragmentation andsize fractionation of single stranded DNA (ssDNA). Homologous fragmentsare hybridized in the absence of polymerase to a complementary ssDNAscaffold. Any overlapping unhybridized fragment ends are trimmed down byan exonuclease. Gaps between fragments are filled in and then ligated togive a pool of full-length diverse strands hybridized to the scaffold,which contains U to preclude amplification. The scaffold then isdestroyed and is replaced by a new strand complementary to the diversestrand by PCR amplification. The method involves one strand (scaffold)that is from only one parent while the priming fragments derive fromother genes, and the parent scaffold is selected against. Thus, noreannealing with parental fragments occurs. Overlapping fragments aretrimmed with an exonuclease. Otherwise, this is conceptually similar toDNA shuffling and StEP. Therefore, there should be no siblings, fewinactives, and no unshuffled parentals. This technique has advantages inthat few or no parental genes are created and many more crossovers canresult relative to standard DNA shuffling.

Recombined Extension on Truncated templates (RETT) entails templateswitching of unidirectionally growing strands from primers in thepresence of unidirectional ssDNA fragments used as a pool of templates(Lee et al., J. Molec. Catalysis 26:119-129 (2003)). No DNAendonucleases are used. Unidirectional ssDNA is made by DNA polymerasewith random primers or serial deletion with exonuclease. UnidirectionalssDNA are only templates and not primers. Random priming andexonucleases do not introduce sequence bias as true of enzymaticcleavage of DNA shuffling/RACHITT. RETT can be easier to optimize thanStEP because it uses normal PCR conditions instead of very shortextensions. Recombination occurs as a component of the PCR steps, thatis, no direct shuffling. This method can also be more random than StEPdue to the absence of pauses.

In Degenerate Oligonucleotide Gene Shuffling (DOGS) degenerate primersare used to control recombination between molecules; (Bergquist andGibbs, Methods Mol. Biol. 352:191-204 (2007); Bergquist et al., Biomol.Eng 22:63-72 (2005); Gibbs et al., Gene 271:13-20 (2001)) this can beused to control the tendency of other methods such as DNA shuffling toregenerate parental genes. This method can be combined with randommutagenesis (epPCR) of selected gene segments. This can be a good methodto block the reformation of parental sequences. No endonucleases areneeded. By adjusting input concentrations of segments made, one can biastowards a desired backbone. This method allows DNA shuffling fromunrelated parents without restriction enzyme digests and allows a choiceof random mutagenesis methods.

Incremental Truncation for the Creation of Hybrid Enzymes (ITCHY)creates a combinatorial library with 1 base pair deletions of a gene orgene fragment of interest (Ostermeier et al., Proc. Natl. Acad. Sci. USA96:3562-3567 (1999); and Ostermeier et al., Nat. Biotechnol.17:1205-1209 (1999)). Truncations are introduced in opposite directionon pieces of 2 different genes. These are ligated together and thefusions are cloned. This technique does not require homology between the2 parental genes. When ITCHY is combined with DNA shuffling, the systemis called SCRATCHY (see below). A major advantage of both is no need forhomology between parental genes; for example, functional fusions betweenan E. coli and a human gene were created via ITCHY. When ITCHY librariesare made, all possible crossovers are captured.

Thio-Incremental Truncation for the Creation of Hybrid Enzymes(THIO-ITCHY) is similar to ITCHY except that phosphothioate dNTPs areused to generate truncations (Lutz et al., Nucleic Acids Res 29:E16(2001)). Relative to ITCHY, THIO-ITCHY can be easier to optimize,provide more reproducibility, and adjustability.

SCRATCHY combines two methods for recombining genes, ITCHY and DNAshuffling (Lutz et al., Proc. Natl. Acad. Sci. USA 98:11248-11253(2001)). SCRATCHY combines the best features of ITCHY and DNA shuffling.First, ITCHY is used to create a comprehensive set of fusions betweenfragments of genes in a DNA homology-independent fashion. Thisartificial family is then subjected to a DNA-shuffling step to augmentthe number of crossovers. Computational predictions can be used inoptimization. SCRATCHY is more effective than DNA shuffling whensequence identity is below 80%.

In Random Drift Mutagenesis (RNDM) mutations are made via epPCR followedby screening/selection for those retaining usable activity (Bergquist etal., Biomol. Eng. 22:63-72 (2005)). Then, these are used in DOGS togenerate recombinants with fusions between multiple active mutants orbetween active mutants and some other desirable parent. Designed topromote isolation of neutral mutations; its purpose is to screen forretained catalytic activity whether or not this activity is higher orlower than in the original gene. RNDM is usable in high throughputassays when screening is capable of detecting activity above background.RNDM has been used as a front end to DOGS in generating diversity. Thetechnique imposes a requirement for activity prior to shuffling or othersubsequent steps; neutral drift libraries are indicated to result inhigher/quicker improvements in activity from smaller libraries. Thoughpublished using epPCR, this could be applied to other large-scalemutagenesis methods.

Sequence Saturation Mutagenesis (SeSaM) is a random mutagenesis methodthat: 1) generates a pool of random length fragments using randomincorporation of a phosphothioate nucleotide and cleavage; this pool isused as a template to 2) extend in the presence of “universal” basessuch as inosine; 3) replication of an inosine-containing complementgives random base incorporation and, consequently, mutagenesis (Wong etal., Biotechnol. J. 3:74-82 (2008); Wong et al., Nucleic Acids Res.32:e26 (2004); and Wong et al., Anal. Biochem. 341:187-189 (2005)).Using this technique it can be possible to generate a large library ofmutants within 2 to 3 days using simple methods. This technique isnon-directed in comparison to the mutational bias of DNA polymerases.Differences in this approach makes this technique complementary (or analternative) to epPCR.

In Synthetic Shuffling, overlapping oligonucleotides are designed toencode “all genetic diversity in targets” and allow a very highdiversity for the shuffled progeny (Ness et al., Nat. Biotechnol.20:1251-1255 (2002)). In this technique, one can design the fragments tobe shuffled. This aids in increasing the resulting diversity of theprogeny. One can design sequence/codon biases to make more distantlyrelated sequences recombine at rates approaching those observed withmore closely related sequences. Additionally, the technique does notrequire physically possessing the template genes.

Nucleotide Exchange and Excision Technology NexT exploits a combinationof dUTP incorporation followed by treatment with uracil DNA glycosylaseand then piperidine to perform endpoint DNA fragmentation (Muller etal., Nucleic Acids Res. 33:e117 (2005)). The gene is reassembled usinginternal PCR primer extension with proofreading polymerase. The sizesfor shuffling are directly controllable using varying dUPT::dTTP ratios.This is an end point reaction using simple methods for uracilincorporation and cleavage. Other nucleotide analogs, such as8-oxo-guanine, can be used with this method. Additionally, the techniqueworks well with very short fragments (86 bp) and has a low error rate.The chemical cleavage of DNA used in this technique results in very fewunshuffled clones.

In Sequence Homology-Independent Protein Recombination (SHIPREC), alinker is used to facilitate fusion between two distantly related orunrelated genes. Nuclease treatment is used to generate a range ofchimeras between the two genes. These fusions result in libraries ofsingle-crossover hybrids (Sieber et al., Nat. Biotechnol. 19:456-460(2001)). This produces a limited type of shuffling and a separateprocess is required for mutagenesis. In addition, since no homology isneeded, this technique can create a library of chimeras with varyingfractions of each of the two unrelated parent genes. SHIPREC was testedwith a heme-binding domain of a bacterial CP450 fused to N-terminalregions of a mammalian CP450; this produced mammalian activity in a moresoluble enzyme.

In Gene Site Saturation Mutagenesis™ (GSSM™) the starting materials area supercoiled dsDNA plasmid containing an insert and two primers whichare degenerate at the desired site of mutations (Kretz et al., MethodsEnzymol. 388:3-11 (2004)). Primers carrying the mutation of interest,anneal to the same sequence on opposite strands of DNA. The mutation istypically in the middle of the primer and flanked on each side byapproximately 20 nucleotides of correct sequence. The sequence in theprimer is NNN or NNK (coding) and MNN (noncoding) (N=all 4, K=G, T, M=A,C). After extension, DpnI is used to digest dam-methylated DNA toeliminate the wild-type template. This technique explores all possibleamino acid substitutions at a given locus (that is, one codon). Thetechnique facilitates the generation of all possible replacements at asingle-site with no nonsense codons and results in equal to near-equalrepresentation of most possible alleles. This technique does not requireprior knowledge of the structure, mechanism, or domains of the targetenzyme. If followed by shuffling or Gene Reassembly, this technologycreates a diverse library of recombinants containing all possiblecombinations of single-site up-mutations. The usefulness of thistechnology combination has been demonstrated for the successfulevolution of over 50 different enzymes, and also for more than oneproperty in a given enzyme.

Combinatorial Cassette Mutagenesis (CCM) involves the use of shortoligonucleotide cassettes to replace limited regions with a large numberof possible amino acid sequence alterations (Reidhaar-Olson et al.Methods Enzymol. 208:564-586 (1991); and Reidhaar-Olson et al. Science241:53-57 (1988)). Simultaneous substitutions at two or three sites arepossible using this technique. Additionally, the method tests a largemultiplicity of possible sequence changes at a limited range of sites.This technique has been used to explore the information content of thelambda repressor DNA-binding domain.

Combinatorial Multiple Cassette Mutagenesis (CMCM) is essentiallysimilar to CCM except it is employed as part of a larger program: 1) useof epPCR at high mutation rate to 2) identify hot spots and hot regionsand then 3) extension by CMCM to cover a defined region of proteinsequence space (Reetz et al., Angew. Chem. Int. Ed Engl. 40:3589-3591(2001)). As with CCM, this method can test virtually all possiblealterations over a target region. If used along with methods to createrandom mutations and shuffled genes, it provides an excellent means ofgenerating diverse, shuffled proteins. This approach was successful inincreasing, by 51-fold, the enantioselectivity of an enzyme.

In the Mutator Strains technique, conditional ts mutator plasmids allowincreases of 20 to 4000-X in random and natural mutation frequencyduring selection and block accumulation of deleterious mutations whenselection is not required (Selifonova et al., Appl. Environ. Microbiol.67:3645-3649 (2001)). This technology is based on a plasmid-derivedmutD5 gene, which encodes a mutant subunit of DNA polymerase III. Thissubunit binds to endogenous DNA polymerase III and compromises theproofreading ability of polymerase III in any strain that harbors theplasmid. A broad-spectrum of base substitutions and frameshift mutationsoccur. In order for effective use, the mutator plasmid should be removedonce the desired phenotype is achieved; this is accomplished through atemperature sensitive (ts) origin of replication, which allows forplasmid curing at 41° C. It should be noted that mutator strains havebeen explored for quite some time (see Low et al., J. Mol. Biol.260:359-3680 (1996)). In this technique, very high spontaneous mutationrates are observed. The conditional property minimizes non-desiredbackground mutations. This technology could be combined with adaptiveevolution to enhance mutagenesis rates and more rapidly achieve desiredphenotypes.

Look-Through Mutagenesis (LTM) is a multidimensional mutagenesis methodthat assesses and optimizes combinatorial mutations of selected aminoacids (Rajpal et al., Proc. Natl. Acad. Sci. USA 102:8466-8471 (2005)).Rather than saturating each site with all possible amino acid changes, aset of nine is chosen to cover the range of amino acid R-groupchemistry. Fewer changes per site allows multiple sites to be subjectedto this type of mutagenesis. A >800-fold increase in binding affinityfor an antibody from low nanomolar to picomolar has been achievedthrough this method. This is a rational approach to minimize the numberof random combinations and can increase the ability to find improvedtraits by greatly decreasing the numbers of clones to be screened. Thishas been applied to antibody engineering, specifically to increase thebinding affinity and/or reduce dissociation. The technique can becombined with either screens or selections.

Gene Reassembly is a DNA shuffling method that can be applied tomultiple genes at one time or to create a large library of chimeras(multiple mutations) of a single gene (Tunable GeneReassembly™ (TGR™)Technology supplied by Verenium Corporation). Typically this technologyis used in combination with ultra-high-throughput screening to query therepresented sequence space for desired improvements. This techniqueallows multiple gene recombination independent of homology. The exactnumber and position of cross-over events can be pre-determined usingfragments designed via bioinformatic analysis. This technology leads toa very high level of diversity with virtually no parental genereformation and a low level of inactive genes. Combined with GSSM™, alarge range of mutations can be tested for improved activity. The methodallows “blending” and “fine tuning” of DNA shuffling, for example, codonusage can be optimized.

In Silico Protein Design Automation (PDA) is an optimization algorithmthat anchors the structurally defined protein backbone possessing aparticular fold, and searches sequence space for amino acidsubstitutions that can stabilize the fold and overall protein energetics(Hayes et al., Proc. Natl. Acad. Sci. USA 99:15926-15931 (2002)). Thistechnology uses in silico structure-based entropy predictions in orderto search for structural tolerance toward protein amino acid variations.Statistical mechanics is applied to calculate coupling interactions ateach position. Structural tolerance toward amino acid substitution is ameasure of coupling. Ultimately, this technology is designed to yielddesired modifications of protein properties while maintaining theintegrity of structural characteristics. The method computationallyassesses and allows filtering of a very large number of possiblesequence variants (1050). The choice of sequence variants to test isrelated to predictions based on the most favorable thermodynamics.Ostensibly only stability or properties that are linked to stability canbe effectively addressed with this technology. The method has beensuccessfully used in some therapeutic proteins, especially inengineering immunoglobulins. In silico predictions avoid testingextraordinarily large numbers of potential variants. Predictions basedon existing three-dimensional structures are more likely to succeed thanpredictions based on hypothetical structures. This technology canreadily predict and allow targeted screening of multiple simultaneousmutations, something not possible with purely experimental technologiesdue to exponential increases in numbers.

Iterative Saturation Mutagenesis (ISM) involves: 1) using knowledge ofstructure/function to choose a likely site for enzyme improvement; 2)performing saturation mutagenesis at chosen site using a mutagenesismethod such as Stratagene QuikChange (Stratagene; San Diego Calif.); 3)screening/selecting for desired properties; and 4) using improvedclone(s), start over at another site and continue repeating until adesired activity is achieved (Reetz et al., Nat. Protoc. 2:891-903(2007); and Reetz et al., Angew. Chem. Int. Ed Engl. 45:7745-7751(2006)). This is a proven methodology, which assures all possiblereplacements at a given position are made for screening/selection.

Any of the aforementioned methods for mutagenesis can be used alone orin any combination. Additionally, any one or combination of the directedevolution methods can be used in conjunction with adaptive evolutiontechniques, as described herein.

It is understood that modifications which do not substantially affectthe activity of the various embodiments of this invention are alsoprovided within the definition of the invention provided herein.Accordingly, the following examples are intended to illustrate but notlimit the present invention.

Example I Pathways for Producing Butadiene or Crotyl Alcohol

Disclosed herein are novel processes for the direct production ofbutadiene or crotyl alcohol using engineered non-natural microorganismsthat possess the enzymes necessary for conversion of common metabolitesinto the four carbon diene, 1,3-butadiene or crotyl alcohol. One novelroute to direct production of butadiene entails reduction of the knownbutanol pathway metabolite crotonyl-CoA to crotyl alcohol via reductionwith aldehyde and alcohol dehydrogenases, followed by phosphorylationwith kinases to afford crotyl pyrophosphate and subsequent conversion tobutadiene using isoprene synthases or variants thereof (see FIG. 2).Another route (FIG. 3) is a variant of the well-characterized DXPpathway for isoprenoid biosynthesis. In this route, the substrate lacksa 2-methyl group and provides butadiene rather than isoprene via abutadiene synthase. Such a butadiene synthase can be derived from aisoprene synthase using methods, such as directed evolution, asdescribed herein. Finally, FIG. 4 shows a pathway to butadiene involvingthe substrate 3-hydroxyglutaryl-CoA, which serves as a surrogate for thenatural mevalonate pathway substrate 3-hydroxy-3-methyl-glutaryl-CoA(shown in FIG. 1). Enzyme candidates for steps A-P of FIG. 2, steps A-Kof FIG. 3 and steps A-O of FIG. 4 are provided below.

Acetyl-CoA:Acetyl-CoA Acyltransferase (FIG. 2, Step A)

Acetoacetyl-CoA thiolase converts two molecules of acetyl-CoA into onemolecule each of acetoacetyl-CoA and CoA. Exemplary acetoacetyl-CoAthiolase enzymes include the gene products of atoB from E. coli (Martinet al., Nat. Biotechnol 21:796-802 (2003)), thlA and thlB from C.acetobutylicum (Hanai et al., Appl Environ Microbiol 73:7814-7818(2007); Winzer et al., J. Mol. Microbiol Biotechnol 2:531-541 (2000)),and ERG10 from S. cerevisiae (Hiser et al., J. Biol. Chem.269:31383-31389 (1994)).

Protein GenBank ID GI number Organism AtoB NP_416728 16130161Escherichia coli ThlA NP_349476.1 15896127 Clostridium acetobutylicumThlB NP_149242.1 15004782 Clostridium acetobutylicum ERG10 NP_0152976325229 Saccharomyces cerevisiae

Acetoacetyl-CoA Reductase (FIG. 2, Step B)

Acetoacetyl-CoA reductase catalyzing the reduction of acetoacetyl-CoA to3-hydroxybutyryl-CoA participates in the acetyl-CoA fermentation pathwayto butyrate in several species of Clostridia and has been studied indetail (Jones et al., Microbiol Rev. 50:484-524 (1986)). The enzyme fromClostridium acetobutylicum, encoded by hbd, has been cloned andfunctionally expressed in E. coli (Youngleson et al., J Bacteriol.171:6800-6807 (1989)). Additionally, subunits of two fatty acidoxidation complexes in E. coli, encoded by fadB and fadJ, function as3-hydroxyacyl-CoA dehydrogenases (Binstock et al., Methods Enzymol. 71Pt C:403-411 (1981)). Yet other gene candidates demonstrated to reduceacetoacetyl-CoA to 3-hydroxybutyryl-CoA are phbB from Zoogloea ramigera(Ploux et al., Eur. J Biochem. 174:177-182 (1988)) and phaB fromRhodobacter sphaeroides (Alber et al., Mol. Microbiol 61:297-309(2006)). The former gene candidate is NADPH-dependent, its nucleotidesequence has been determined (Peoples et al., Mol. Microbiol 3:349-357(1989)) and the gene has been expressed in E. coli. Substratespecificity studies on the gene led to the conclusion that it couldaccept 3-oxopropionyl-CoA as a substrate besides acetoacetyl-CoA (Plouxet al., supra, (1988)). Additional gene candidates include Hbd1(C-terminal domain) and Hbd2 (N-terminal domain) in Clostridium kluyveri(Hillmer and Gottschalk, Biochim. Biophys. Acta 3334:12-23 (1974)) andHSD17B10 in Bos taurus (WAKIL et al., J Biol. Chem. 207:631-638 (1954)).

Protein Genbank ID GI number Organism fadB P21177.2 119811 Escherichiacoli fadJ P77399.1 3334437 Escherichia coli Hbd2 EDK34807.1 146348271Clostridium kluyveri Hbd1 EDK32512.1 146345976 Clostridium kluyveri hbdP52041.2 18266893 Clostridium acetobutylicum HSD17B10 O02691.3 3183024Bos Taurus phbB P23238.1 130017 Zoogloea ramigera phaB YP_353825.177464321 Rhodobacter sphaeroides

A number of similar enzymes have been found in other species ofClostridia and in Metallosphaera sedula (Berg et al., Science.318:1782-1786 (2007)).

Protein GenBank ID GI number Organism hbd NP_349314.1 NP_349314.1Clostridium acetobutylicum hbd AAM14586.1 AAM14586.1 Clostridiumbeijerinckii Msed_1423 YP_001191505 YP_001191505 Metallosphaera sedulaMsed_0399 YP_001190500 YP_001190500 Metallosphaera sedula Msed_0389YP_001190490 YP_001190490 Metallosphaera sedula Msed_1993 YP_001192057YP_001192057 Metallosphaera sedula

3-Hydroxybutyryl-CoA Dehydratase (FIG. 2, Step C)

3-Hydroxybutyryl-CoA dehydratase (EC 4.2.1.55), also called crotonase,is an enoyl-CoA hydratase that reversibly dehydrates3-hydroxybutyryl-CoA to form crotonyl-CoA. Crotonase enzymes arerequired for n-butanol formation in some organisms, particularlyClostridial species, and also comprise one step of the3-hydroxypropionate/4-hydroxybutyrate cycle in thermoacidophilic Archaeaof the genera Sulfolobus, Acidianus, and Metallosphaera. Exemplary genesencoding crotonase enzymes can be found in C. acetobutylicum (Atsumi etal., Metab Eng. 10:305-311 (2008); Boynton et al., J Bacteriol.178:3015-3024 (1996)), C. kluyveri (Hillmer et al., FEBS Lett.21:351-354 (1972)), and Metallosphaera sedula (Berg et al., Science318:1782-1786 (2007a)) though the sequence of the latter gene is notknown. The enoyl-CoA hydratase of Pseudomonas putida, encoded by ech,catalyzes the conversion of crotonyl-CoA to 3-hydroxybutyryl-CoA(Roberts et al., Arch Microbiol. 117:99-108 (1978)). Additionalenoyl-CoA hydratase candidates are phaA and phaB, of P. putida, and paaAand paaB from P. fluorescens (Olivera et al., Proc. Natl. Acad. SciU.S.A 95:6419-6424 (1998)). Lastly, a number of Escherichia coli geneshave been shown to demonstrate enoyl-CoA hydratase functionalityincluding maoC (Park et al., J Bacteriol. 185:5391-5397 (2003)), paaF(Ismail et al., Eur. J. Biochem. 270:3047-3054 (2003); Park et al.,Appl. Biochem. Biotechnol 113-116:335-346 (2004); Park et al.,Biotechnol Bioeng 86:681-686 (2004)) and paaG (Ismail et al., supra,(2003); Park and Lee, supra, (2004); Park and Yup, supra, (2004)). Theseproteins are identified below.

Protein GenBank ID GI Number Organism crt NP_349318.1 15895969Clostridium acetobutylicum crt1 YP_001393856.1 153953091 Clostridiumkluyveri ech NP_745498.1 26990073 Pseudomonas putida paaA NP_745427.126990002 Pseudomonas putida paaB NP_745426.1 26990001 Pseudomonas putidaphaA ABF82233.1 106636093 Pseudomonas fluorescens phaB ABF82234.1106636094 Pseudomonas fluorescens maoC NP_415905.1 16129348 Escherichiacoli paaF NP_415911.1 16129354 Escherichia coli paaG NP_415912.116129355 Escherichia coli

Crotonyl-CoA Reductase (Aldehyde Forming) (FIG. 2, Step D)

Several acyl-CoA dehydrogenases are capable of reducing an acyl-CoA toits corresponding aldehyde. Thus they can naturally reduce crotonyl-CoAto crotonaldehyde or can be engineered to do so. Exemplary genes thatencode such enzymes include the Acinetobacter Calcoaceticus acr1encoding a fatty acyl-CoA reductase (Reiser et al., J. Bacteriol.179:2969-2975 (1997)), the Acinetobacter sp. M-1 fatty acyl-CoAreductase (Ishige et al., Appl. Environ. Microbiol. 68:1192-1195(2002)), and a CoA- and NADP-dependent succinate semialdehydedehydrogenase encoded by the sucD gene in Clostridium kluyveri (Sohlinget., J Bacteriol. 178:871-880 (1996); Sohling et al., J. Bacteriol.178:871-80 (1996))). SucD of P. gingivalis is another succinatesemialdehyde dehydrogenase (Takahashi et al., J. Bacteriol.182:4704-4710 (2000)). These succinate semialdehyde dehydrogenases werespecifically shown in ref. (Burk et al., WO/2008/115840: (2008)) toconvert 4-hydroxybutyryl-CoA to 4-hydroxybutanal as part of a pathway toproduce 1,4-butanediol. The enzyme acylating acetaldehyde dehydrogenasein Pseudomonas sp, encoded by bphG, is yet another capable enzyme as ithas been demonstrated to oxidize and acylate acetaldehyde,propionaldehyde, butyraldehyde, isobutyraldehyde and formaldehyde(Powlowski et al., J. Bacteriol. 175:377-385 (1993)).

Protein GenBank ID GI Number Organism acr1 YP_047869.1 50086359Acinetobacter calcoaceticus acr1 AAC45217 1684886 Acinetobacter baylyiacr1 BAB85476.1 18857901 Acinetobacter sp. Strain M-1 sucD P38947.1172046062 Clostridium kluyveri sucD NP_904963.1 34540484 Porphyromonasgingivalis bphG BAA03892.1 425213 Pseudomonas sp

An additional enzyme type that converts an acyl-CoA to its correspondingaldehyde is malonyl-CoA reductase which transforms malonyl-CoA tomalonic semialdehyde. Malonyl-CoA reductase is a key enzyme inautotrophic carbon fixation via the 3-hydroxypropionate cycle inthermoacidophilic archael bacteria (Berg et al., Science 318:1782-1786(2007b); Thauer, 318:1732-1733 (2007)). The enzyme utilizes NADPH as acofactor and has been characterized in Metallosphaera and Sulfolobus spp(Alber et al., J. Bacteriol. 188:8551-8559 (2006); Hugler et al., J.Bacteriol. 184:2404-2410 (2002)). The enzyme is encoded by Msed_(—)0709in Metallosphaera sedula (Alber et al., supra, (2006); Berg et al.,supra, (2007b)). A gene encoding a malonyl-CoA reductase from Sulfolobustokodaii was cloned and heterologously expressed in E. coli (Alber etal., supra, (2006)). Although the aldehyde dehydrogenase functionalityof these enzymes is similar to the bifunctional dehydrogenase fromChloroflexus aurantiacus, there is little sequence similarity. Bothmalonyl-CoA reductase enzyme candidates have high sequence similarity toaspartate-semialdehyde dehydrogenase, an enzyme catalyzing the reductionand concurrent dephosphorylation of aspartyl-4-phosphate to aspartatesemialdehyde. Additional gene candidates can be found by sequencehomology to proteins in other organisms including Sulfolobussolfataricus and Sulfolobus acidocaldarius. Yet another candidate forCoA-acylating aldehyde dehydrogenase is the ald gene from Clostridiumbeijerinckii (Toth, Appl. Environ. Microbiol. 65:4973-4980 (1999). Thisenzyme has been reported to reduce acetyl-CoA and butyryl-CoA to theircorresponding aldehydes. This gene is very similar to eutE that encodesacetaldehyde dehydrogenase of Salmonella typhimurium and E. coli (Toth,Appl. Environ. Microbiol. 65:4973-4980 (1999). These proteins areidentified below.

Protein GenBank ID GI Number Organism Msed_0709 YP_001190808.1 146303492Metallosphaera sedula Mcr NP_378167.1 15922498 Sulfolobus tokodaii asd-2NP_343563.1 15898958 Sulfolobus solfataricus Saci_2370 YP_256941.170608071 Sulfolobus acidocaldarius Ald AAT66436 49473535 Clostridiumbeijerinckii eutE AAA80209 687645 Salmonella typhimurium eutE P774452498347 Escherichia coli

Crotonaldehyde Reductase (Alcohol Forming) (FIG. 2, Step E)

Enzymes exhibiting crotonaldehyde reductase (alcohol forming) activityare capable of forming crotyl alcohol from crotonaldehyde. The followingenzymes can naturally possess this activity or can be engineered toexhibit this activity. Exemplary genes encoding enzymes that catalyzethe conversion of an aldehyde to alcohol (i.e., alcohol dehydrogenase orequivalently aldehyde reductase) include alrA encoding a medium-chainalcohol dehydrogenase for C₂-C₁₄ (Tani et al., Appl. Environ. Microbiol.66:5231-5235 (2000)), ADH2 from Saccharomyces cerevisiae (Atsumi et al.,Nature 451:86-89 (2008)), yqhD from E. coli which has preference formolecules longer than C(3) (Sulzenbacher et al., J. Mol. Biol.342:489-502 (2004)), and bdh I and bdh II from C. acetobutylicum whichconverts butyraldehyde into butanol (Walter et al., J. Bacteriol.174:7149-7158 (1992)). ADH1 from Zymomonas mobilis has been demonstratedto have activity on a number of aldehydes including formaldehyde,acetaldehyde, propionaldehyde, butyraldehyde, and acrolein (Kinoshita,Appl. Microbiol. Biotechnol. 22:249-254 (1985)). Cbei_(—)2181 fromClostridium beijerinckii NCIMB 8052 encodes yet another useful alcoholdehydrogenase capable of converting crotonaldehyde to crotyl alcohol.

Protein GenBank ID GI Number Organism alrA BAB12273.1 9967138Acinetobacter sp. Strain M-1 ADH2 NP_014032.1 6323961 Saccharomycescerevisiae yqhD NP_417484.1 16130909 Escherichia coli bdh I NP_349892.115896543 Clostridium acetobutylicum bdh II NP_349891.1 15896542Clostridium acetobutylicum adhA YP_162971.1 56552132 Zymomonas mobilisCbei_2181 YP_001309304.1 150017050 Clostridium beijerinckii NCIMB 8052

Enzymes exhibiting 4-hydroxybutyrate dehydrogenase activity (EC1.1.1.61) also fall into this category. Such enzymes have beencharacterized in Ralstonia eutropha (Bravo et al., J. Forensic Sci.49:379-387 (2004)), Clostridium kluyveri (Wolff et al., Protein Expr.Purif. 6:206-212 (1995)) and Arabidopsis thaliana (Breitkreuz et al., J.Biol. Chem. 278:41552-41556 (2003)).

Protein GenBank ID GI Number Organism 4hbd YP_726053.1 113867564Ralstonia eutropha H16 4hbd L21902.1 146348486 Clostridium kluyveri DSM555 4hbd Q94B07 75249805 Arabidopsis thaliana

Crotyl Alcohol Kinase (FIG. 2, Step F)

Crotyl alcohol kinase enzymes catalyze the transfer of a phosphate groupto the hydroxyl group of crotyl alcohol. The enzymes described belownaturally possess such activity or can be engineered to exhibit thisactivity. Kinases that catalyze transfer of a phosphate group to analcohol group are members of the EC 2.7.1 enzyme class. The table belowlists several useful kinase enzymes in the EC 2.7.1 enzyme class.

Enzyme Commission Number Enzyme Name 2.7.1.1 hexokinase 2.7.1.2glucokinase 2.7.1.3 ketohexokinase 2.7.1.4 fructokinase 2.7.1.5rhamnulokinase 2.7.1.6 galactokinase 2.7.1.7 mannokinase 2.7.1.8glucosamine kinase 2.7.1.10 phosphoglucokinase 2.7.1.116-phosphofructokinase 2.7.1.12 gluconokinase 2.7.1.13dehydrogluconokinase 2.7.1.14 sedoheptulokinase 2.7.1.15 ribokinase2.7.1.16 ribulokinase 2.7.1.17 xylulokinase 2.7.1.18 phosphoribokinase2.7.1.19 phosphoribulokinase 2.7.1.20 adenosine kinase 2.7.1.21thymidine kinase 2.7.1.22 ribosylnicotinamide kinase 2.7.1.23 NAD+kinase 2.7.1.24 dephospho-CoA kinase 2.7.1.25 adenylyl-sulfate kinase2.7.1.26 riboflavin kinase 2.7.1.27 erythritol kinase 2.7.1.28triokinase 2.7.1.29 glycerone kinase 2.7.1.30 glycerol kinase 2.7.1.31glycerate kinase 2.7.1.32 choline kinase 2.7.1.33 pantothenate kinase2.7.1.34 pantetheine kinase 2.7.1.35 pyridoxal kinase 2.7.1.36mevalonate kinase 2.7.1.39 homoserine kinase 2.7.1.40 pyruvate kinase2.7.1.41 glucose-1-phosphate phosphodismutase 2.7.1.42 riboflavinphosphotransferase 2.7.1.43 glucuronokinase 2.7.1.44 galacturonokinase2.7.1.45 2-dehydro-3- deoxygluconokinase 2.7.1.46 L-arabinokinase2.7.1.47 D-ribulokinase 2.7.1.48 uridine kinase 2.7.1.49hydroxymethylpyrimidine kinase 2.7.1.50 hydroxyethylthiazole kinase2.7.1.51 L-fuculokinase 2.7.1.52 fucokinase 2.7.1.53 L-xylulokinase2.7.1.54 D-arabinokinase 2.7.1.55 allose kinase 2.7.1.561-phosphofructokinase 2.7.1.58 2-dehydro-3- deoxygalactonokinase2.7.1.59 N-acetylglucosamine kinase 2.7.1.60 N-acylmannosamine kinase2.7.1.61 acyl-phosphate-hexose phosphotransferase 2.7.1.62phosphoramidate-hexose phosphotransferase 2.7.1.63 polyphosphate-glucosephosphotransferase 2.7.1.64 inositol 3-kinase 2.7.1.65 scyllo-inosamine4-kinase 2.7.1.66 undecaprenol kinase 2.7.1.67 1-phosphatidylinositol 4-kinase 2.7.1.68 1-phosphatidylinositol-4- phosphate 5-kinase 2.7.1.69protein-Np- phosphohistidine-sugar phosphotransferase 2.7.1.70 identicalto EC 2.7.1.37. 2.7.1.71 shikimate kinase 2.7.1.72 streptomycin 6-kinase2.7.1.73 inosine kinase 2.7.1.74 deoxycytidine kinase 2.7.1.76deoxyadenosine kinase 2.7.1.77 nucleoside phosphotransferase 2.7.1.78polynucleotide 5′-hydroxyl- kinase 2.7.1.79 diphosphate-glycerolphosphotransferase 2.7.1.80 diphosphate-serine phosphotransferase2.7.1.81 hydroxylysine kinase 2.7.1.82 ethanolamine kinase 2.7.1.83pseudouridine kinase 2.7.1.84 alkylglycerone kinase 2.7.1.85 β-glucosidekinase 2.7.1.86 NADH kinase 2.7.1.87 streptomycin 3″-kinase 2.7.1.88dihydrostreptomycin-6- phosphate 3′a-kinase 2.7.1.89 thiamine kinase2.7.1.90 diphosphate-fructose-6- phosphate 1- phosphotransferase2.7.1.91 sphinganine kinase 2.7.1.92 5-dehydro-2- deoxygluconokinase2.7.1.93 alkylglycerol kinase 2.7.1.94 acylglycerol kinase 2.7.1.95kanamycin kinase 2.7.1.100 S-methyl-5-thioribose kinase 2.7.1.101tagatose kinase 2.7.1.102 hamamelose kinase 2.7.1.103 viomycin kinase2.7.1.105 6-phosphofructo-2-kinase 2.7.1.106 glucose-1,6-bisphosphatesynthase 2.7.1.107 diacylglycerol kinase 2.7.1.108 dolichol kinase2.7.1.113 deoxyguanosine kinase 2.7.1.114 AMP-thymidine kinase 2.7.1.118ADP-thymidine kinase 2.7.1.119 hygromycin-B 7″-O-kinase 2.7.1.121phosphoenolpyruvate- glycerone phosphotransferase 2.7.1.122 xylitolkinase 2.7.1.127 inositol-trisphosphate 3- kinase 2.7.1.130tetraacyldisaccharide 4′- kinase 2.7.1.134 inositol-tetrakisphosphate1-kinase 2.7.1.136 macrolide 2′-kinase 2.7.1.137 phosphatidylinositol 3-kinase 2.7.1.138 ceramide kinase 2.7.1.140 inositol-tetrakisphosphate5-kinase 2.7.1.142 glycerol-3-phosphate- glucose phosphotransferase2.7.1.143 diphosphate-purine nucleoside kinase 2.7.1.144tagatose-6-phosphate kinase 2.7.1.145 deoxynucleoside kinase 2.7.1.146ADP-dependent phosphofructokinase 2.7.1.147 ADP-dependent glucokinase2.7.1.148 4-(cytidine 5′-diphospho)- 2-C-methyl-D-erythritol kinase2.7.1.149 1-phosphatidylinositol-5- phosphate 4-kinase 2.7.1.1501-phosphatidylinositol-3- phosphate 5-kinase 2.7.1.151inositol-polyphosphate multikinase 2.7.1.153 phosphatidylinositol-4,5-bisphosphate 3-kinase 2.7.1.154 phosphatidylinositol-4- phosphate3-kinase 2.7.1.156 adenosylcobinamide kinase 2.7.1.157N-acetylgalactosamine kinase 2.7.1.158 inositol-pentakisphosphate2-kinase 2.7.1.159 inositol-1,3,4-trisphosphate 5/6-kinase 2.7.1.1602′-phosphotransferase 2.7.1.161 CTP-dependent riboflavin kinase2.7.1.162 N-acetylhexosamine 1- kinase 2.7.1.163 hygromycin B 4-O-kinase2.7.1.164 O-phosphoseryl-tRNASec kinase

A good candidate for this step is mevalonate kinase (EC 2.7.1.36) thatphosphorylates the terminal hydroxyl group of the methyl analog,mevalonate, of 3,5-dihydroxypentanote. Some gene candidates for thisstep are erg12 from S. cerevisiae, mvk from Methanocaldococcusjannaschi, MVK from Homo sapeins, and mvk from Arabidopsis thaliana col.

Protein GenBank ID GI Number Organism erg12 CAA39359.1 3684Sachharomyces cerevisiae mvk Q58487.1 2497517 Methanocaldococcusjannaschii mvk AAH16140.1 16359371 Homo sapiens M\mvk NP_851084.130690651 Arabidopsis thaliana

Glycerol kinase also phosphorylates the terminal hydroxyl group inglycerol to form glycerol-3-phosphate. This reaction occurs in severalspecies, including Escherichia coli, Saccharomyces cerevisiae, andThermotoga maritima. The E. coli glycerol kinase has been shown toaccept alternate substrates such as dihydroxyacetone and glyceraldehyde(Hayashi et al., J Biol. Chem. 242:1030-1035 (1967)). T, maritime hastwo glycerol kinases (Nelson et al., Nature 399:323-329 (1999)).Glycerol kinases have been shown to have a wide range of substratespecificity. Crans and Whiteside studied glycerol kinases from fourdifferent organisms (Escherichia coli, S. cerevisiae, Bacillusstearothermophilus, and Candida mycoderma) (Crans et al., J. Am. Chem.Soc. 107:7008-7018 (2010); Nelson et al., supra, (1999)). They studied66 different analogs of glycerol and concluded that the enzyme couldaccept a range of substituents in place of one terminal hydroxyl groupand that the hydrogen atom at C2 could be replaced by a methyl group.Interestingly, the kinetic constants of the enzyme from all fourorganisms were very similar. The gene candidates are:

Protein GenBank ID GI Number Organism glpK AP_003883.1 89110103Escherichia coli K12 glpK1 NP_228760.1 15642775 Thermotoga maritime MSB8glpK2 NP_229230.1 15642775 Thermotoga maritime MSB8 Gut1 NP_011831.182795252 Saccharomyces cerevisiae

Homoserine kinase is another possible candidate that can lead to thephosphorylation of 3,5-dihydroxypentanoate. This enzyme is also presentin a number of organisms including E. coli, Streptomyces sp, and S.cerevisiae. Homoserine kinase from E. coli has been shown to haveactivity on numerous substrates, including, L-2-amino,1,4-butanediol,aspartate semialdehyde, and 2-amino-5-hydroxyvalerate (Huo et al.,Biochemistry 35:16180-16185 (1996); Huo et al., Arch. Biochem. Biophys.330:373-379 (1996)). This enzyme can act on substrates where thecarboxyl group at the alpha position has been replaced by an ester or bya hydroxymethyl group. The gene candidates are:

Protein GenBank ID GI Number Organism thrB BAB96580.2 85674277Escherichia coli K12 SACT1DRAFT_4809 ZP_06280784.1 282871792Streptomyces sp. ACT-1 Thr1 AAA35154.1 172978 Saccharomyces serevisiae

2-Butenyl-4-Phosphate Kinase (FIG. 2, Step G)

2-Butenyl-4-phosphate kinase enzymes catalyze the transfer of aphosphate group to the phosphate group of 2-butenyl-4-phosphate. Theenzymes described below naturally possess such activity or can beengineered to exhibit this activity. Kinases that catalyze transfer of aphosphate group to another phosphate group are members of the EC 2.7.4enzyme class. The table below lists several useful kinase enzymes in theEC 2.7.4 enzyme class.

Enzyme Commission Number Enzyme Name 2.7.4.1 polyphosphate kinase2.7.4.2 phosphomevalonate kinase 2.7.4.3 adenylate kinase 2.7.4.4nucleoside-phosphate kinase 2.7.4.6 nucleoside-diphosphate kinase2.7.4.7 phosphomethylpyrimidine kinase 2.7.4.8 guanylate kinase 2.7.4.9dTMP kinase 2.7.4.10 nucleoside-triphosphate-adenylate kinase 2.7.4.11(deoxy)adenylate kinase 2.7.4.12 T2-induced deoxynucleotide kinase2.7.4.13 (deoxy)nucleoside-phosphate kinase 2.7.4.14 cytidylate kinase2.7.4.15 thiamine-diphosphate kinase 2.7.4.16 thiamine-phosphate kinase2.7.4.17 3-phosphoglyceroyl-phosphate-polyphosphate phosphotransferase2.7.4.18 farnesyl-diphosphate kinase 2.7.4.195-methyldeoxycytidine-5′-phosphate kinase 2.7.4.20dolichyl-diphosphate-polyphosphate phosphotransferase 2.7.4.21inositol-hexakisphosphate kinase 2.7.4.22 UMP kinase 2.7.4.23 ribose1,5-bisphosphate phosphokinase 2.7.4.24diphosphoinositol-pentakisphosphate kinase

Phosphomevalonate kinase enzymes are of particular interest.Phosphomevalonate kinase (EC 2.7.4.2) catalyzes the analogoustransformation to 2-butenyl-4-phosphate kinase. This enzyme is encodedby erg8 in Saccharomyces cerevisiae (Tsay et al., Mol. Cell Biol.11:620-631 (1991)) and mvaK2 in Streptococcus pneumoniae, Staphylococcusaureus and Enterococcus faecalis (Doun et al., Protein Sci. 14:1134-1139(2005); Wilding et al., J Bacteriol. 182:4319-4327 (2000)). TheStreptococcus pneumoniae and Enterococcus faecalis enzymes were clonedand characterized in E. coli (Pilloff et al., J Biol. Chem.278:4510-4515 (2003); Doun et al., Protein Sci. 14:1134-1139 (2005)).

Protein GenBank ID GI Number Organism Erg8 AAA34596.1 171479Saccharomyces cerevisiae mvaK2 AAG02426.1 9937366 Staphylococcus aureusmvaK2 AAG02457.1 9937409 Streptococcus pneumoniae mvaK2 AAG02442.19937388 Enterococcus faecalis

Butadiene Synthase (FIG. 2, Step H)

Butadiene synthase catalyzes the conversion of 2-butenyl-4-diphosphateto 1,3-butadiene. The enzymes described below naturally possess suchactivity or can be engineered to exhibit this activity. Isoprenesynthase naturally catalyzes the conversion of dimethylallyl diphosphateto isoprene, but can also catalyze the synthesis of 1,3-butadiene from2-butenyl-4-diphosphate. Isoprene synthases can be found in severalorganisms including Populus alba (Sasaki et al., FEBS Letters, 2005, 579(11), 2514-2518), Pueraria montana (Lindberg et al., Metabolic Eng,2010, 12 (1), 70-79; Sharkey et al., Plant Physiol., 2005, 137 (2),700-712), and Populus tremula×Populus alba (Miller et al., Planta, 2001,213 (3), 483-487). Additional isoprene synthase enzymes are described in(Chotani et al., WO/2010/031079, Systems Using Cell Culture forProduction of Isoprene; Cervin et al., US Patent Application20100003716, Isoprene Synthase Variants for Improved MicrobialProduction of Isoprene).

Protein GenBank ID GI Number Organism ispS BAD98243.1 63108310 Populusalba ispS AAQ84170.1 35187004 Pueraria montana ispS CAC35696.1 13539551Populus tremula × Populus alba

Crotonyl-CoA Hydrolase, Synthetase, Transferase (FIG. 2, Step I)

Crotonyl-CoA hydrolase catalyzes the conversion of crotonyl-CoA tocrotonate. The enzymes described below naturally possess such activityor can be engineered to exhibit this activity. 3-Hydroxyisobutyryl-CoAhydrolase efficiently catalyzes the conversion of3-hydroxyisobutyryl-CoA to 3-hydroxyisobutyrate during valinedegradation (Shimomura et al., J Biol. Chem. 269:14248-14253 (1994)).Genes encoding this enzyme include hibch of Rattus norvegicus (Shimomuraet al., supra; Shimomura et al., Methods Enzymol. 324:229-240 (2000))and Homo sapiens (Shimomura et al., supra). The H. sapiens enzyme alsoaccepts 3-hydroxybutyryl-CoA and 3-hydroxypropionyl-CoA as substrates(Shimomura et al., supra). Candidate genes by sequence homology includehibch of Saccharomyces cerevisiae and BC_(—)2292 of Bacillus cereus.These proteins are identified below.

Protein GenBank ID GI Number Organism hibch Q5XIE6.2 146324906 Rattusnorvegicus hibch Q6NVY1.2 146324905 Homo sapiens hibch P28817.2 2506374Saccharomyces cerevisiae BC_2292 AP09256 29895975 Bacillus cereus

Several eukaryotic acetyl-CoA hydrolases (EC 3.1.2.1) have broadsubstrate specificity and thus represent suitable candidate enzymes. Forexample, the enzyme from Rattus norvegicus brain (Robinson et al., Res.Commun. 71:959-965 (1976)) can react with but 1-CoA, hexanoyl-CoA andmalonyl-CoA. Though its sequence has not been reported, the enzyme fromthe mitochondrion of the pea leaf also has a broad substratespecificity, with demonstrated activity on acetyl-CoA, propionyl-CoA,butyryl-CoA, palmitoyl-CoA, oleoyl-CoA, succinyl-CoA, and crotonyl-CoA(Zeiher et al., Plant. Physiol. 94:20-27 (1990)). The acetyl-CoAhydrolase, ACH1, from S. cerevisiae represents another candidatehydrolase (Buu et al., J. Biol. Chem. 278:17203-17209 (2003)). Theseproteins are identified below.

Protein GenBank ID GI Number Organism acot12 NP_570103.1 18543355 Rattusnorvegicus ACH1 NP_009538 6319456 Saccharomyces cerevisiae

Another candidate hydrolase is the human dicarboxylic acid thioesterase,acot8, which exhibits activity on glutaryl-CoA, adipyl-CoA, suberyl-CoA,sebacyl-CoA, and dodecanedioyl-CoA (Westin et al., J. Biol. Chem.280:38125-38132 (2005)) and the closest E. coli homolog, tesB, which canalso hydrolyze a broad range of CoA thioesters (Naggert et al., J. Biol.Chem. 266:11044-11050 (1991)). A similar enzyme has also beencharacterized in the rat liver (Deana et al., Biochem. Int. 26:767-773(1992)). Other potential E. coli thioester hydrolases include the geneproducts of tesA (Bonner et al., Chem. 247:3123-3133 (1972)), ybgC(Kuznetsova et al., FEMS Microbiol Rev 29:263-279 (2005); and (Zhuang etal., FEBS Lett. 516:161-163 (2002)), paaI (Song et al., J. Biol. Chem.281:11028-11038 (2006)), and ybdB (Leduc et al., J. Bacteriol.189:7112-7126 (2007)). These proteins are identified below.

Protein GenBank ID GI Number Organism tesB NP_414986 16128437Escherichia coli acot8 CAA15502 3191970 Homo sapiens acot8 NP_57011251036669 Rattus norvegicus tesA NP_415027 16128478 Escherichia coli ybgCNP_415264 16128711 Escherichia coli paaI NP_415914 16129357 Escherichiacoli ybdB NP_415129 16128580 Escherichia coli

Yet another candidate hydrolase is the glutaconate CoA-transferase fromAcidaminococcus fermentans. This enzyme was transformed by site-directedmutagenesis into an acyl-CoA hydrolase with activity on glutaryl-CoA,acetyl-CoA and 3-butenoyl-CoA (Mack et al., FEBS. Lett. 405:209-212(1997)). This suggests that the enzymes encodingsuccinyl-CoA:3-ketoacid-CoA transferases and acetoacetyl-CoA:acetyl-CoAtransferases can also serve as candidates for this reaction step butwould require certain mutations to change their function. These proteinsare identified below.

Protein GenBank ID GI Number Organism gctA CAA57199 559392Acidaminococcus fermentans gctB CAA57200 559393 Acidaminococcusfermentans

Crotonyl-CoA synthetase catalyzes the conversion of crotonyl-CoA tocrotonate. The enzymes described below naturally possess such activityor can be engineered to exhibit this activity. One candidate enzyme,ADP-forming acetyl-CoA synthetase (ACD, EC 6.2.1.13), couples theconversion of acyl-CoA esters to their corresponding acids with theconcurrent synthesis of ATP. Several enzymes with broad substratespecificities have been described in the literature. ACD I fromArchaeoglobus fulgidus, encoded by AF1211, was shown to operate on avariety of linear and branched-chain substrates including acetyl-CoA,propionyl-CoA, butyryl-CoA, acetate, propionate, butyrate, isobutyryate,isovalerate, succinate, fumarate, phenylacetate, indoleacetate (Musfeldtet al., J Bacteriol 184:636-644 (2002)). The enzyme from Haloarculamarismortui (annotated as a succinyl-CoA synthetase) accepts propionate,butyrate, and branched-chain acids (isovalerate and isobutyrate) assubstrates, and was shown to operate in the forward and reversedirections (Brasen et al., Arch Microbiol 182:277-287 (2004)). The ACDencoded by PAE3250 from hyperthermophilic crenarchaeon Pyrobaculumaerophilum showed the broadest substrate range of all characterizedACDs, reacting with acetyl-CoA, isobutyryl-CoA (preferred substrate) andphenylacetyl-CoA (Brasen et al., supra). The enzymes from A. fulgidus,H. marismortui and P. aerophilum have all been cloned, functionallyexpressed, and characterized in E. coli (Musfeldt et al., supra; Brasenet al., supra). These proteins are identified below.

Protein GenBank ID GI Number Organism AF1211 NP_070039.1 11498810Archaeoglobus fulgidus DSM 4304 scs YP_135572.1 55377722 Haloarculamarismortui ATCC 43049 PAE3250 NP_560604.1 18313937 Pyrobaculumaerophilum str. IM2

Another candidate CoA synthetase is succinyl-CoA synthetase. The sucCDgenes of E. coli form a succinyl-CoA synthetase complex which naturallycatalyzes the formation of succinyl-CoA from succinate with theconcaminant consumption of one ATP, a reaction which is reversible invivo (Buck et al., Biochem. 24:6245-6252 (1985)). These proteins areidentified below.

Protein GenBank ID GI Number Organism sucC NP_415256.1 16128703Escherichia coli sucD AAC73823.1 1786949 Escherichia coli

Additional exemplary CoA-ligases include the rat dicarboxylate-CoAligase for which the sequence is yet uncharacterized (Vamecq et al.,Biochemical Journal 230:683-693 (1985)), either of the two characterizedphenylacetate-CoA ligases from P. chrysogenum (Lamas-Maceiras et al.,Biochem. J. 395:147-155 (2005); Wang et al., Biochem Biophy Res Commun360(2):453-458 (2007)), the phenylacetate-CoA ligase from Pseudomonasputida (Martinez-Blanco et al., J. Biol. Chem. 265:7084-7090 (1990)),and the 6-carboxyhexanoate-CoA ligase from Bacillus subtilis (Boweretal., J. Bacteriol. 178(14):4122-4130 (1996)). Additional candidateenzymes are acetoacetyl-CoA synthetases from Mus musculus (Hasegawa etal., Biochim Biophys Acta 1779:414-419 (2008)) and Homo sapiens (Ohgamiet al., Biochem Pharmacol 65:989-994 (2003)) which naturally catalyzethe ATP-dependant conversion of acetoacetate into acetoacetyl-CoA. Theseproteins are identified below.

Protein GenBank ID GI Number Organism phl CAJ15517.1 77019264Penicillium chrysogenum phlB ABS19624.1 152002983 Penicilliumchrysogenum paaF AAC24333.2 22711873 Pseudomonas putida bioW NP_390902.250812281 Bacillus subtilis AACS NP_084486.1 21313520 Mus musculus AACSNP_076417.2 31982927 Homo sapiens

Crotonyl-CoA transferase catalyzes the conversion of crotonyl-CoA tocrotonate. The enzymes described below naturally possess such activityor can be engineered to exhibit this activity. Many transferases havebroad specificity and thus can utilize CoA acceptors as diverse asacetate, succinate, propionate, butyrate, 2-methylacetoacetate,3-ketohexanoate, 3-ketopentanoate, valerate, crotonate,3-mercaptopropionate, propionate, vinylacetate, butyrate, among others.For example, an enzyme from Roseburia sp. A2-183 was shown to havebutyryl-CoA: acetate: CoA transferase and propionyl-CoA: acetate: CoAtransferase activity (Charrier et al., Microbiology 152, 179-185(2006)). Close homologs can be found in, for example, Roseburiaintestinalis L1-82, Roseburia inulinivorans DSM 16841, Eubacteriumrectale ATCC 33656. Another enzyme with propionyl-CoA transferaseactivity can be found in Clostridium propionicum (Selmer et al., Eur JBiochem 269, 372-380 (2002)). This enzyme can use acetate, (R)-lactate,(S)-lactate, acrylate, and butyrate as the CoA acceptor (Selmer et al.,Eur J Biochem 269, 372-380 (2002); Schweiger and Buckel, FEBS Letters,171(1) 79-84 (1984)). Close homologs can be found in, for example,Clostridium novyi NT, Clostridium beijerinckii NCIMB 8052, andClostridium botulinum C str. Eklund. YgfH encodes a propionylCoA:succinate CoA transferase in E. coli (Haller et al., Biochemistry,39(16) 4622-4629). Close homologs can be found in, for example,Citrobacter youngae ATCC 29220, Salmonella enterica subsp. arizonaeserovar, and Yersinia intermedia ATCC 29909. These proteins areidentified below.

Protein GenBank ID GI Number Organism Ach1 AAX19660.1 60396828 Roseburiasp. A2-183 ROSINTL182_07121 ZP_04743841.2 257413684 Roseburiaintestinalis L1-82 ROSEINA2194_03642 ZP_03755203.1 225377982 Roseburiainulinivorans DSM 16841 EUBREC_3075 YP_002938937.1 238925420 Eubacteriumrectale ATCC 33656 pct CAB77207.1 7242549 Clostridium propionicumNT01CX_2372 YP_878445.1 118444712 Clostridium novyi NT Cbei_4543YP_001311608.1 150019354 Clostridium beijerinckii NCIMB 8052 CBC_A0889ZP_02621218.1 168186583 Clostridium botulinum C str. Eklund ygfHNP_417395.1 16130821 Escherichia coli str. K-12 substr. MG1655CIT292_04485 ZP_03838384.1 227334728 Citrobacter youngae ATCC 29220SARI_04582 YP_001573497.1 161506385 Salmonella enterica subsp. arizonaeserovar yinte0001_14430 ZP_04635364.1 238791727 Yersinia intermedia ATCC29909

An additional candidate enzyme is the two-unit enzyme encoded by pcaIand pcaJ in Pseudomonas, which has been shown to have3-oxoadipyl-CoA/succinate transferase activity (Kaschabek et al.,supra). Similar enzymes based on homology exist in Acinetobacter sp.ADP1 (Kowalchuk et al., Gene 146:23-30 (1994)) and Streptomycescoelicolor. Additional exemplary succinyl-CoA:3:oxoacid-CoA transferasesare present in Helicobacter pylori (Corthesy-Theulaz et al., J. Biol.Chem. 272:25659-25667 (1997)) and Bacillus subtilis (Stols et al.,Protein. Expr. Purif. 53:396-403 (2007)). These proteins are identifiedbelow.

Protein GenBank ID GI Number Organism pcaI AAN69545.1 24985644Pseudomonas putida pcaJ NP_746082.1 26990657 Pseudomonas putida pcaIYP_046368.1 50084858 Acinetobacter sp. ADP1 pcaJ AAC37147.1 141776Acinetobacter sp. ADP1 pcaI NP_630776.1 21224997 Streptomyces coelicolorpcaJ NP_630775.1 21224996 Streptomyces coelicolor HPAG1_0676 YP_627417108563101 Helicobacter pylori HPAG1_0677 YP_627418 108563102Helicobacter pylori ScoA NP_391778 16080950 Bacillus subtilis ScoBNP_391777 16080949 Bacillus subtilis

A CoA transferase that can utilize acetate as the CoA acceptor isacetoacetyl-CoA transferase, encoded by the E. coli atoA (alpha subunit)and atoD (beta subunit) genes (Vanderwinkel et al., Biochem. Biophys.Res Commun. 33:902-908 (1968); Korolev et al., Acta Crystallogr. D BiolCrystallogr. 58:2116-2121 (2002)). This enzyme has also been shown totransfer the CoA moiety to acetate from a variety of branched and linearacyl-CoA substrates, including isobutyrate (Matthies et al., ApplEnviron Microbiol 58:1435-1439 (1992)), valerate (Vanderwinkel et al.,supra) and butanoate (Vanderwinkel et al., supra). Similar enzymes existin Corynebacterium glutamicum ATCC 13032 (Duncan et al., Appl EnvironMicrobiol 68:5186-5190 (2002)), Clostridium acetobutylicum (Cary et al.,Appl Environ Microbiol 56:1576-1583 (1990)), and Clostridiumsaccharoperbutylacetonicum (Kosaka et al., Biosci. Biotechnol Biochem.71:58-68 (2007)). These proteins are identified below.

Protein GenBank ID GI Number Organism atoA P76459.1 2492994 Escherichiacoli K12 atoD P76458.1 2492990 Escherichia coli K12 actA YP_226809.162391407 Corynebacterium glutamicum ATCC 13032 cg0592 YP_224801.162389399 Corynebacterium glutamicum ATCC 13032 ctfA NP_149326.1 15004866Clostridium acetobutylicum ctfB NP_149327.1 15004867 Clostridiumacetobutylicum ctfA AAP42564.1 31075384 Clostridiumsaccharoperbutylacetonicum ctfB AAP42565.1 31075385 Clostridiumsaccharoperbutylacetonicum

The above enzymes can also exhibit the desired activities oncrotonyl-CoA. Additional exemplary transferase candidates are catalyzedby the gene products of cat1, cat2, and cat3 of Clostridium kluyveriwhich have been shown to exhibit succinyl-CoA, 4-hydroxybutyryl-CoA, andbutyryl-CoA transferase activity, respectively (Seedorf et al., supra;Sohling et al., Eur. J Biochem. 212:121-127 (1993); Sohling et al., JBacteriol. 178:871-880 (1996)). Similar CoA transferase activities arealso present in Trichomonas vaginalis (van Grinsven et al., J. Biol.Chem. 283:1411-1418 (2008)) and Trypanosoma brucei (Riviere et al., J.Biol. Chem. 279:45337-45346 (2004)). These proteins are identifiedbelow.

Protein GenBank ID GI Number Organism cat1 P38946.1 729048 Clostridiumkluyveri cat2 P38942.2 172046066 Clostridium kluyveri cat3 EDK35586.1146349050 Clostridium kluyveri TVAG_395550 XP_001330176 123975034Trichomonas vaginalis G3 Tb11.02.0290 XP_828352 71754875 Trypanosomabrucei

The glutaconate-CoA-transferase (EC 2.8.3.12) enzyme from anaerobicbacterium Acidaminococcus fermentans reacts with diacid glutaconyl-CoAand 3-butenoyl-CoA (Mack et al., FEBS Lett. 405:209-212 (1997)). Thegenes encoding this enzyme are gctA and gctB. This enzyme has reducedbut detectable activity with other CoA derivatives includingglutaryl-CoA, 2-hydroxyglutaryl-CoA, adipyl-CoA and acrylyl-CoA (Buckelet al., Eur. J. Biochem. 118:315-321 (1981)). The enzyme has been clonedand expressed in E. coli (Mack et al., Eur. J. Biochem. 226:41-51(1994)). These proteins are identified below.

Protein GenBank ID GI Number Organism gctA CAA57199.1 559392Acidaminococcus fermentans gctB CAA57200.1 559393 Acidaminococcusfermentans

Crotonate Reductase (FIG. 2, Step J)

Crotonate reductase enzymes are capable of catalyzing the conversion ofcrotonate to crotonaldehyde. The enzymes described below naturallypossess such activity or can be engineered to exhibit this activity.Carboxylic acid reductase catalyzes the magnesium, ATP andNADPH-dependent reduction of carboxylic acids to their correspondingaldehydes (Venkitasubramanian et al., J. Biol. Chem. 282:478-485(2007)). This enzyme, encoded by car, was cloned and functionallyexpressed in E. coli (Venkitasubramanian et al., J. Biol. Chem.282:478-485 (2007)). Expression of the npt gene product improvedactivity of the enzyme via post-transcriptional modification. The nptgene encodes a specific phosphopantetheine transferase (PPTase) thatconverts the inactive apo-enzyme to the active holo-enzyme. The naturalsubstrate of this enzyme is vanillic acid, and the enzyme exhibits broadacceptance of aromatic and aliphatic substrates (Venkitasubramanian etal., in Biocatalysis in the Pharmaceutical and Biotechnology Industires,ed. R.N. Patel, Chapter 15, pp. 425-440, CRC Press LLC, Boca Raton, Fla.(2006)).

Protein GenBank ID GI Number Organism Car AAR91681.1 40796035 Nocardiaiowensis (sp. NRRL 5646) Npt ABI83656.1 114848891 Nocardia iowensis (sp.NRRL 5646)

Additional car and npt genes can be identified based on sequencehomology.

Protein GenBank ID GI Number Organism fadD9 YP_978699.1 121638475Mycobacterium bovis BCG BCG_2812c YP_978898.1 121638674 Mycobacteriumbovis BCG nfa20150 YP_118225.1 54023983 Nocardia farcinica IFM 10152nfa40540 YP_120266.1 54026024 Nocardia farcinica IFM 10152 SGR_6790YP_001828302.1 182440583 Streptomyces griseus subsp. griseus NBRC 13350SGR_665 YP_001822177.1 182434458 Streptomyces griseus subsp. griseusNBRC 13350 MSMEG_2956 YP_887275.1 118473501 Mycobacterium smegmatis MC2155 MSMEG_5739 YP_889972.1 118469671 Mycobacterium smegmatis MC2 155MSMEG_2648 YP_886985.1 118471293 Mycobacterium smegmatis MC2 155MAP1040c NP_959974.1 41407138 Mycobacterium avium subsp.paratuberculosis K-10 MAP2899c NP_961833.1 41408997 Mycobacterium aviumsubsp. paratuberculosis K-10 MMAR_2117 YP_001850422.1 183982131Mycobacterium marinum M MMAR_2936 YP_001851230.1 183982939 Mycobacteriummarinum M MMAR_1916 YP_001850220.1 183981929 Mycobacterium marinum MTpauDRAFT_33060 ZP_04027864.1 227980601 Tsukamurella paurometabola DSM20162 TpauDRAFT_20920 ZP_04026660.1 227979396 Tsukamurella paurometabolaDSM 20162 CPCC7001_1320 ZP_05045132.1 254431429 Cyanobium PCC7001DDBDRAFT_0187729 XP_636931.1 66806417 Dictyostelium discoideum AX4

An additional enzyme candidate found in Streptomyces griseus is encodedby the griC and griD genes. This enzyme is believed to convert3-amino-4-hydroxybenzoic acid to 3-amino-4-hydroxybenzaldehyde asdeletion of either griC or griD led to accumulation of extracellular3-acetylamino-4-hydroxybenzoic acid, a shunt product of3-amino-4-hydroxybenzoic acid metabolism (Suzuki, et al., J. Antibiot.60(6):380-387 (2007)). Co-expression of griC and griD with SGR_(—)665,an enzyme similar in sequence to the Nocardia iowensis npt, can bebeneficial.

Protein GenBank ID GI Number Organism griC YP_001825755.1 182438036Streptomyces griseus subsp. griseus NBRC 13350 Grid YP_001825756.1182438037 Streptomyces griseus subsp. griseus NBRC 13350

An enzyme with similar characteristics, alpha-aminoadipate reductase(AAR, EC 1.2.1.31), participates in lysine biosynthesis pathways in somefungal species. This enzyme naturally reduces alpha-aminoadipate toalpha-aminoadipate semialdehyde. The carboxyl group is first activatedthrough the ATP-dependent formation of an adenylate that is then reducedby NAD(P)H to yield the aldehyde and AMP. Like CAR, this enzyme utilizesmagnesium and requires activation by a PPTase. Enzyme candidates for AARand its corresponding PPTase are found in Saccharomyces cerevisiae(Morris et al., Gene 98:141-145 (1991)), Candida albicans (Guo et al.,Mol. Genet. Genomics 269:271-279 (2003)), and Schizosaccharomyces pombe(Ford et al., Curr. Genet. 28:131-137 (1995)). The AAR from S. pombeexhibited significant activity when expressed in E. coli (Guo et al.,Yeast 21:1279-1288 (2004)). The AAR from Penicillium chrysogenum acceptsS-carboxymethyl-L-cysteine as an alternate substrate, but did not reactwith adipate, L-glutamate or diaminopimelate (Hijarrubia et al., J.Biol. Chem. 278:8250-8256 (2003)). The gene encoding the P. chrysogenumPPTase has not been identified to date.

Protein GenBank ID GI Number Organism LYS2 AAA34747.1 171867Saccharomyces cerevisiae LYS5 P50113.1 1708896 Saccharomyces cerevisiaeLYS2 AAC02241.1 2853226 Candida albicans LYS5 AAO26020.1 28136195Candida albicans Lys1p P40976.3 13124791 Schizosaccharomyces pombe Lys7pQ10474.1 1723561 Schizosaccharomyces pombe Lys2 CAA74300.1 3282044Penicillium chrysogenum

Crotonyl-CoA Reductase (Alcohol Forming) (FIG. 2, Step K)

Crotonaldehyde reductase (alcohol forming) enzymes catalyze the 2reduction steps required to form crotyl alcohol from crotonyl-CoA.Exemplary 2-step oxidoreductases that convert an acyl-CoA to an alcoholare provided below. Such enzymes can naturally convert crotonyl-CoA tocrotyl alcohol or can be engineered to do so. These enzymes includethose that transform substrates such as acetyl-CoA to ethanol (e.g.,adhE from E. coli (Kessler et al., FEBS. Lett. 281:59-63 (1991))) andbutyryl-CoA to butanol (e.g. adhE2 from C. acetobutylicum (Fontaine etal., J. Bacteriol. 184:821-830 (2002))). The adhE2 enzyme from C.acetobutylicum was specifically shown in ref. (Burk et al., supra,(2008)) to produce BDO from 4-hydroxybutyryl-CoA. In addition toreducing acetyl-CoA to ethanol, the enzyme encoded by adhE inLeuconostoc mesenteroides has been shown to oxide the branched chaincompound isobutyraldehyde to isobutyryl-CoA (Kazahaya et al., J. Gen.Appl. Microbiol. 18:43-55 (1972); Koo et al., Biotechnol. Lett.27:505-510 (2005)).

Protein GenBank ID GI Number Organism adhE NP_415757.1 16129202Escherichia coli adhE2 AAK09379.1 12958626 Clostridium acetobutylicumadhE AAV66076.1 55818563 Leuconostoc mesenteroides

Another exemplary enzyme can convert malonyl-CoA to 3-HP. AnNADPH-dependent enzyme with this activity has characterized inChloroflexus aurantiacus where it participates in the3-hydroxypropionate cycle (Hugler et al., supra, (2002); Strauss et al.,215:633-643 (1993)). This enzyme, with a mass of 300 kDa, is highlysubstrate-specific and shows little sequence similarity to other knownoxidoreductases (Hugler et al., supra, (2002)). No enzymes in otherorganisms have been shown to catalyze this specific reaction; howeverthere is bioinformatic evidence that other organisms can have similarpathways (Klatt et al., Environ Microbiol. 9:2067-2078 (2007)). Enzymecandidates in other organisms including Roseiflexus castenholzii,Erythrobacter sp. NAP1 and marine gamma proteobacterium HTCC2080 can beinferred by sequence similarity.

Protein GenBank ID GI Number Organism mcr AAS20429.1 42561982Chloroflexus aurantiacus Rcas_2929 YP_001433009.1 156742880 Roseiflexuscastenholzii NAP1_02720 ZP_01039179.1 85708113 Erythrobacter sp. NAP1MGP2080_00535 ZP_01626393.1 119504313 marine gamma proteobacteriumHTCC2080

Glutaconyl-CoA Decarboxylase (FIG. 2, Step L)

Glutaconyl-CoA decarboxylase enzymes, characterized inglutamate-fermenting anaerobic bacteria, are sodium-ion translocatingdecarboxylases that utilize biotin as a cofactor and are composed offour subunits (alpha, beta, gamma, and delta) (Boiangiu et al., J. Mol.Microbiol Biotechnol 10:105-119 (2005); Buckel, Biochim Biophys Acta.1505:15-27 (2001)). Such enzymes have been characterized inFusobacterium nucleatum (Beatrix et al., Arch Microbiol. 154:362-369(1990)) and Acidaminococcus fermentans (Braune et al., Mol. Microbiol31:473-487 (1999)). Analogs to the F. nucleatum glutaconyl-CoAdecarboxylase alpha, beta and delta subunits are found in S.aciditrophicus. A gene annotated as an enoyl-CoA dehydrogenase,syn_(—)00480, another GCD, is located in a predicted operon between abiotin-carboxyl carrier (syn_(—)00479) and a glutaconyl-CoAdecarboxylase alpha subunit (syn_(—)00481). The protein sequences forexemplary gene products can be found using the following GenBankaccession numbers shown below.

Protein GenBank ID GI Number Organism gcdA CAA49210 49182Acidaminococcus fermentans gcdC AAC69172 3777506 Acidaminococcusfermentans gcdD AAC69171 3777505 Acidaminococcus fermentans gcdBAAC69173 3777507 Acidaminococcus fermentans FN0200 AAL94406 19713641Fusobacterium nucleatum FN0201 AAL94407 19713642 Fusobacterium nucleatumFN0204 AAL94410 19713645 Fusobacterium nucleatum syn_00479 YP_46206685859864 Syntrophus aciditrophicus syn_00481 YP_462068 85859866Syntrophus aciditrophicus syn_01431 YP_460282 85858080 Syntrophusaciditrophicus syn_00480 ABC77899 85722956 Syntrophus aciditrophicus

Glutaryl-CoA Dehydrogenase (FIG. 2 Step M)

Glutaryl-CoA dehydrogenase (GCD, EC 1.3.99.7 and EC 4.1.1.70) is abifunctional enzyme that catalyzes the oxidative decarboxylation ofglutaryl-CoA to crotonyl-CoA (FIG. 3, step 3). Bifunctional GCD enzymesare homotetramers that utilize electron transfer flavoprotein as anelectron acceptor (Hartel et al., Arch Microbiol. 159:174-181 (1993)).Such enzymes were first characterized in cell extracts of Pseudomonasstrains KB740 and K172 during growth on aromatic compounds (Hartel etal., supra, (1993)), but the associated genes in these organisms isunknown. Genes encoding glutaryl-CoA dehydrogenase (gcdH) and itscognate transcriptional regulator (gcdR) were identified in Azoarcus sp.CIB (Blazquez et al., Environ Microbiol. 10:474-482 (2008)). An Azoarcusstrain deficient in gcdH activity was used to identify the aheterologous gene gcdH from Pseudomonas putida (Blazquez et al., supra,(2008)). The cognate transcriptional regulator in Pseudomonas putida hasnot been identified but the locus PP_(—)0157 has a high sequencehomology (>69% identity) to the Azoarcus enzyme. Additional GCD enzymesare found in Pseudomonas fluorescens and Paracoccus denitrificans(Husain et al., J. Bacteriol. 163:709-715 (1985)). The human GCD hasbeen extensively studied, overexpressed in E. coli (Dwyer et al.,Biochemistry 39:11488-11499 (2000)), crystallized, and the catalyticmechanism involving a conserved glutamate residue in the active site hasbeen described (Fu et al., Biochemistry 43:9674-9684 (2004)). A GCD inSyntrophus aciditrophicus operates in the CO₂-assimilating directionduring growth on crotonate (Mouttaki et al., Appl Environ Microbiol.73:930-938 (2007))). Two GCD genes in S. aciditrophicus were identifiedby protein sequence homology to the Azoarcus GcdH: syn_(—)00480 (31%)and syn_(—)01146 (31%). No significant homology was found to theAzoarcus GcdR regulatory protein. The protein sequences for exemplarygene products can be found using the following GenBank accession numbersshown below.

Protein GenBank ID GI Number Organism gcdH ABM69268.1 123187384 Azoarcussp. CIB gcdR ABM69269.1 123187385 Azoarcus sp. CIB gcdH AAN65791.124981507 Pseudomonas putida KT2440 PP_0157 AAN65790.1 24981506Pseudomonas putida (gcdR) KT2440 gcdH YP_257269.1 70733629 Pseudomonasfluorescens Pf-5 gcvA (gcdR) YP_257268.1 70733628 Pseudomonasfluorescens Pf-5 gcd YP_918172.1 119387117 Paracoccus denitrificans gcdRYP_918173.1 119387118 Paracoccus denitrificans gcd AAH02579.1 12803505Homo sapiens syn_00480 ABC77899 85722956 Syntrophus aciditrophicussyn_01146 ABC76260 85721317 Syntrophus aciditrophicus

3-Aminobutyryl-CoA Deaminase (FIG. 2, Step N)

3-aminobutyryl-CoA is an intermediate in lysine fermentation. It alsocan be formed from acetoacetyl-CoA via a transaminase or an aminatingdehydrogenase. 3-aminobutyryl-CoA deaminase (or 3-aminobutyryl-CoAammonia lyase) catalyzes the deamination of 3-aminobutyryl-CoA to formcrotonyl-CoA. This reversible enzyme is present in Fusobacteriumnucleatum, Porphyromonas gingivalis, Thermoanaerobacter tengcongensis,and several other organisms and is co-localized with several genesinvolved. in lysine fermentation (Kreirneyer et al., J Biol Chem, 2007,282(10) 7191-7197).

Protein GenBank ID GI Number Organism kal NP_602669.1 19705174Fusobacterium nucleatum subsp. nucleatum ATCC 25586 kal NP_905282.134540803 Porphyromonas gingivalis W83 kal NP_622376.1 20807205Thermoanaerobacter tengcongensis MB4

4-Hydroxybutyryl-CoA Dehydratase (FIG. 2, Step O)

Several enzymes naturally catalyze the dehydration of4-hydroxybutyryl-CoA to crotonoyl-CoA. This transformation is requiredfor 4-aminobutyrate fermentation by Clostridium aminobutyricum (Scherfet al., Eur. J. Biochem. 215:421-429 (1993)) and succinate-ethanolfermentation by Clostridium kluyveri (Scherf et al., Arch. Microbiol161:239-245 (1994)). The transformation is also a key step in Archaea,for example, Metallosphaera sedula, as part of the3-hydroxypropionate/4-hydroxybutyrate autotrophic carbon dioxideassimilation pathway (Berg et al., supra, (2007)). The reversibility of4-hydroxybutyryl-CoA dehydratase is well-documented (Muh et al.,Biochemistry. 35:11710-11718 (1996); Friedrich et al., Angew. Chem. Int.Ed. Engl. 47:3254-3257 (2008); Muh et al., Eur. J. Biochem. 248:380-384(1997)) and the equilibrium constant has been reported to be about 4 onthe side of crotonoyl-CoA (Scherf and Buckel, supra, (1993)).

Protein GenBank ID GI Number Organism AbfD CAB60035 70910046 Clostridiumaminobutyricum AbfD YP_001396399 153955634 Clostridium kluyveriMsed_1321 YP_001191403 146304087 Metallosphaera sedula Msed_1220YP_001191305 146303989 Metallosphaera sedula

Crotyl Alcohol Diphosphokinase (FIG. 2, Step P)

Crotyl alcohol diphosphokinase enzymes catalyze the transfer of adiphosphate group to the hydroxyl group of crotyl alcohol. The enzymesdescribed below naturally possess such activity or can be engineered toexhibit this activity. Kinases that catalyze transfer of a diphosphategroup are members of the EC 2.7.6 enzyme class. The table below listsseveral useful kinase enzymes in the EC 2.7.6 enzyme class.

Enzyme Commission Number Enzyme Name 2.7.6.1 ribose-phosphatediphosphokinase 2.7.6.2 thiamine diphosphokinase 2.7.6.32-amino-4-hydroxy-6- hydroxymethyldihydropteridine diphosphokinase2.7.6.4 nucleotide diphosphokinase 2.7.6.5 GTP diphosphokinase

Of particular interest are ribose-phosphate diphosphokinase enzymeswhich have been identified in Escherichia coli (Hove-Jenson et al., JBiol Chem, 1986, 261(15); 6765-71) and Mycoplasma pneumoniae M129(McElwain et al, International Journal of Systematic Bacteriology, 1988,38:417-423) as well as thiamine diphosphokinase enzymes. Exemplarythiamine diphosphokinase enzymes are found in Arabidopsis thaliana(Ajjawi, Plant Mol Biol, 2007, 65(1-2); 151-62).

Protein GenBank ID GI Number Organism prs NP_415725.1 16129170Escherichia coli prsA NP_109761.1 13507812 Mycoplasma pneumoniae M129TPK1 BAH19964.1 222424006 Arabidopsis thaliana col TPK2 BAH57065.1227204427 Arabidopsis thaliana col

Erythrose-4-Phosphate Reductase (FIG. 3, Step A)

In Step A of the pathway, erythrose-4-phosphate is converted toerythritol-4-phosphate by the erythrose-4-phosphate reductase orerythritol-4-phosphate dehydrogenase. The reduction oferythrose-4-phosphate was observed in Leuconostoc oenos during theproduction of erythritol (Veiga-da-Cunha et al., J Bacteriol.175:3941-3948 (1993)). NADPH was identified as the cofactor(Veiga-da-Cunha et al., supra, (1993)). However, gene forerythrose-4-phosphate was not identified. Thus, it is possible toidentify the erythrose-4-phosphate reductase gene from Leuconostoc oenosand apply to this step. Additionally, enzymes catalyzing similarreactions can be utilized for this step. An example of these enzymes is1-deoxy-D-xylulose-5-phosphate reductoisomerase (EC 1.1.1.267)catalyzing the conversion of 1-deoxy-D-xylylose 5-phosphate to2-C-methyl-D-erythritol-4-phosphate, which has one additional methylgroup comparing to Step A. The dxr or ispC genes encode the1-deoxy-D-xylulose-5-phosphate reductoisomerase have been well studied:the Dxr proteins from Escherichia coli and Mycobacterium tuberculosiswere purified and their crystal structures were determined (Yajima etal., Acta Crystallogr. Sect. F. Struct. Biol. Cryst. Commun. 63:466-470(2007); Mac et al., J Mol. Biol. 345:115-127 (2005); Henriksson et al.,Acta Crystallogr. D. Biol. Crystallogr. 62:807-813 (2006); Henriksson etal., J Biol. Chem. 282:19905-19916 (2007)); the Dxr protein fromSynechocystis sp was studied by site-directed mutagenesis with modifiedactivity and altered kinetics (Fernandes et al., Biochim. Biophys. Acta1764:223-229 (2006); Fernandes et al., Arch. Biochem. Biophys.444:159-164 (2005)). Furthermore, glyceraldehyde 3-phosphate reductaseYghZ from Escherichia coli catalyzes the conversion betweenglyceraldehyde 3-phosphate and glycerol-3-phosphate (Desai et al.,Biochemistry 47:7983-7985 (2008)) can also be applied to this step. Thefollowing genes can be used for Step A conversion:

Protein GenBank ID GI Number Organism dxr P45568.2 2506592 Escherichiacoli strain K12 dxr A5U6M4.1 166218269 Mycobacterium tuberculosis dxrQ55663.1 2496789 Synechocystis sp. strain PCC6803 yghZ NP_417474.116130899 Escherichia coli strain K12

Erythritol-4-Phospate Cytidylyltransferase (FIG. 3, Step B)

In Step B of the pathway, erythritol-4-phosphate is converted to4-(cytidine 5′-diphospho)-erythritol by the erythritol-4-phospatecytidylyltransferase or 4-(cytidine 5′-diphospho)-erythritol synthase.The exact enzyme for this step has not been identified. However, enzymescatalyzing similar reactions can be applied to this step. An example isthe 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase or4-(cytidine 5′-diphospho)-2-C-methyl-D-erythritol synthase (EC2.7.7.60). The 2-C-methyl-D-erythritol 4-phospate cytidylyltransferaseis in the methylerythritol phosphate pathway for the isoprenoidbiosynthesis and catalyzes the conversion between2-C-methyl-D-erythritol 4-phospate and 4-(cytidine5′-diphospho)-2-C-methyl-D-erythritol, with an extra methyl groupcomparing to Step B conversion. The 2-C-methyl-D-erythritol 4-phosphatecytidylyltransferase is encoded by ispD gene and the crystal structureof Escherichia coli IspD was determined (Kemp et al., Acta Crystallogr.D. Biol. Crystallogr. 57:1189-1191 (2001); Kemp et al., ActaCrystallogr. D. Biol. Crystallogr. 59:607-610 (2003); Richard et al.,Nat. Struct. Biol. 8:641-648 (2001)). The ispD gene from Mycobacteriumtuberculosis H37Rv was cloned and expressed in Escherichia coli, and therecombinant proteins were purified with N-terminal His-tag (Shi et al.,Biochem. Mol. Biol. 40:911-920 (2007)). Additionally, the Streptomycescoelicolor ispD gene was cloned and expressed in E. coli, and therecombinant proteins were characterized physically and kinetically (Caneet al., Bioorg. Med. Chem. 9:1467-1477 (2001)). The following genes canbe used for Step B conversion:

Protein GenBank ID GI Number Organism ispD Q46893.3 2833415 Escherichiacoli strain K12 ispD A5U8Q7.1 166215456 Mycobacterium tuberculosis ispDQ9L0Q8.1 12230289 Streptomyces coelicolor

4-(Cytidine 5′-diphospho)-erythritol kinase (FIG. 3, Step C)

In Step C of the pathway, 4-(cytidine 5′-diphospho)-erythritol isconverted to 2-phospho-4-(cytidine 5′-diphospho)-erythritol by the4-(cytidine 5′-diphospho)-erythritol kinase. The exact enzyme for thisstep has not been identified. However, enzymes catalyzing similarreactions can be applied to this step. An example is the4-diphosphocytidyl-2-C-methylerythritol kinase (EC 2.7.1.148). The4-diphosphocytidyl-2-C-methylerythritol kinase is also in themethylerythritol phosphate pathway for the isoprenoid biosynthesis andcatalyzes the conversion between 4-(cytidine5′-diphospho)-2-C-methyl-D-erythritol and 2-phospho-4-(cytidine5′-diphospho)-2-C-methyl-D-erythritol, with an extra methyl groupcomparing to Step C conversion. The4-diphosphocytidyl-2-C-methylerythritol kinase is encoded by ispE geneand the crystal structures of Escherichia coli, Thermos thermophilusHB8, and Aquifex aeolicus IspE were determined (Sgraja et al., FEBS J275:2779-2794 (2008); Miallau et al., Proc. Natl. Acad. Sci. U.S.A100:9173-9178 (2003); Wada et al., J. Biol. Chem. 278:30022-30027(2003)). The ispE genes from above organism were cloned and expressed,and the recombinant proteins were purified for crystallization. Thefollowing genes can be used for Step C conversion:

Protein GenBank ID GI Number Organism ispE P62615.1 50402174 Escherichiacoli strain K12 ispE P83700.1 51316201 Thermus thermophilus HB8 ispEO67060.1 6919911 Aquifex aeolicus

Erythritol 2,4-Cyclodiphosphate Synthase (FIG. 3, Step D)

In Step D of the pathway, 2-phospho-4-(cytidine 5′-diphospho)-erythritolis converted to erythritol-2,4-cyclodiphosphate by the Erythritol2,4-cyclodiphosphate synthase. The exact enzyme for this step has notbeen identified. However, enzymes catalyzing similar reactions can beapplied to this step. An example is the 2-C-methyl-D-erythritol2,4-cyclodiphosphate synthase (EC 4.6.1.12). The 2-C-methyl-D-erythritol2,4-cyclodiphosphate synthase is also in the methylerythritol phosphatepathway for the isoprenoid biosynthesis and catalyzes the conversionbetween 2-phospho-4-(cytidine 5′ diphospho)-2-C-methyl-D-erythritol and2-C-methyl-D-erythritol-2,4-cyclodiphosphate, with an extra methyl groupcomparing to step D conversion. The 2-C-methyl-D-erythritol2,4-cyclodiphosphate synthase is encoded by ispF gene and the crystalstructures of Escherichia coli, Thermus thermophilus, Haemophilusinfluenzae, and Campylobacter jejuni IspF were determined (Richard etal., J Biol. Chem. 277:8667-8672 (2002); Steinbacher et al., J Mol.Biol. 316:79-88 (2002); Lehmann et al., Proteins 49:135-138 (2002);Kishida et al., Acta Crystallogr. D. Biol. Crystallogr. 59:23-31 (2003);Gabrielsen et al., J. Biol. Chem. 279:52753-52761 (2004)). The ispFgenes from above organism were cloned and expressed, and the recombinantproteins were purified for crystallization. The following genes can beused for Step D conversion:

Protein GenBank ID GI Number Organism ispF P62617.1 51317402 Escherichiacoli strain K12 ispF Q8RQP5.1 51701599 Thermus thermophilus HB8 ispFP44815.1 1176081 Haemophilus influenzae ispF Q9PM68.1 12230305Campylobacter jejuni

1-Hydroxy-2-Butenyl 4-Diphosphate Synthase (FIG. 3, Step E)

Step E of FIG. 3 entails conversion of erythritol-2,4-cyclodiphosphateto 1-hydroxy-2-butenyl 4-diphosphate by 1-hydroxy-2-butenyl4-diphosphate synthase. An enzyme with this activity has not beencharacterized to date. This transformation is analogous to the reductionof 2-C-methyl-D-erythritol-2,4-cyclodiphosphate to1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate by(E)-4-hydroxy-3-methylbut-2-enyl-diphosphate synthase (EC 1.17.7.1).This enzyme is an iron-sulfur protein that participates in thenon-mevalonate pathway for isoprenoid biosynthesis found in bacteria andplants. Most bacterial enzymes including the E. coli enzyme, encoded byispG, utilize reduced ferredoxin or flavodoxin as an electron donor(Zepeck et al., J. Org. Chem. 70:9168-9174 (2005)). An analogous enzymefrom the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1,encoded by gcpE, was heterologously expressed and characterized in E.coli (Okada et al., J Biol. Chem. 280:20672-20679 (2005)). Additionalenzyme candidates from Thermus thermophilus and Arabidopsis thalianahave been characterized and expressed in E. coli (Seemann et al., JBiol. Inorg. Chem. 10:131-137 (2005); Kollas et al., FEBS Lett.532:432-436 (2002)).

Protein GenBank ID GI Number Organism ispG NP_417010.1 16130440Escherichia coli gcpE NP_681786.1 22298539 Thermosynechococcus elongatusgcpE AAO21364.1 27802077 Thermus thermophilus gcpE AAO15446.1 27462472Arabidopsis thaliana

1-Hydroxy-2-Butenyl 4-Diphosphate Reductase (FIG. 3, Step F)

The concurrent dehydration and reduction of 1-hydroxy-2-butenyl4-diphosphate is catalyzed by an enzyme with 1-hydroxy-2-butenyl4-diphosphate reductase activity (FIG. 3, Step F). Such an enzyme willform a mixture of products, butenyl 4-diphosphate or 2-butenyl4-diphosphate. An analogous reaction is catalyzed by4-hydroxy-3-methylbut-2-enyl diphosphate reductase (EC 1.17.1.2) in thenon-mevalonate pathway for isoprenoid biosynthesis. This enzyme is aniron-sulfur protein that utilizes reduced ferredoxin or flavodoxin as anelectron donor. Maximal activity of 4-hydroxy-3-methylbut-2-enyldiphosphate reductase E. coli, encoded by ispH, requires both flavodoxinand flavodoxin reductase (Wolff et al., FEBS Lett. 541:115-120 (2003);Grawert et al., J Am. Chem. Soc. 126:12847-12855 (2004)). In thecharacterized catalytic system, reduced flavodoxin is regenerated by theNAD(P)+-dependent flavodoxin reductase. The enzyme from Aquifexaeolicus, encoded by lytB, was expressed as a His-tagged enzyme in E.coli and characterized (Altincicek et al., FEBS Lett. 532:437-440(2002)). An analogous enzyme in plants is encoded by hdr of Arabidopsisthaliana (Botella-Pavia et al., Plant J 40:188-199 (2004)).

Protein GenBank ID GI Number Organism ispH AAL38655.1 18652795Escherichia coli lytB O67625.1 8928180 Aquifex aeolicus hdr NP_567965.118418433 Arabidopsis thaliana

Altering the expression level of genes involved in iron-sulfur clusterformation can have an advantageous effect on the activities ofiron-sulfur proteins in the proposed pathways (for example, enzymesrequired in Steps E and F of FIG. 3). In E. coli, it was demonstratedthat overexpression of the iron-sulfur containing protein IspH(analogous to Step F of FIG. 3) is enhanced by coexpression of genesfrom the isc region involved in assembly of iron-sulfur clusters(Grawert et al., J Am. Chem. Soc. 126:12847-12855 (2004)). The genecluster is composed of the genes icsS, icsU, icsA, hscB, hscA and fdx.Overexpression of these genes was shown to improve the syntheticcapability of the iron-sulfur assembly pipeline, required for functionalexpression of iron-sulfur proteins. A similar approach can be applicablein the current application.

Protein GenBank ID GI Number Organism iscS AAT48142.1 48994898Escherichia coli iscU AAC75582.1 1788878 Escherichia coli iscAAAC75581.1 1788877 Escherichia coli hscB AAC75580.1 1788876 Escherichiacoli hscA AAC75579.1 1788875 Escherichia coli fdx AAC75578.1 1788874Escherichia coli

Butenyl 4-Diphosphate Isomerase (FIG. 3, Step G)

Butenyl 4-diphosphate isomerase catalyzes the reversible interconversionof 2-butenyl-4-diphosphate and butenyl-4-diphosphate. The followingenzymes can naturally possess this activity or can be engineered toexhibit this activity. Useful genes include those that encode enzymesthat interconvert isopenenyl diphosphate and dimethylallyl diphosphate.These include isopentenyl diphosphate isomerase enzymes from Escherichiacoli (Rodríguez-Concepción et al., FEBS Lett, 473(3):328-332),Saccharomyces cerevisiae (Anderson et al., J Biol Chem, 1989, 264(32);19169-75), and Sulfolobus shibatae (Yamashita et al, Eur J Biochem,2004, 271(6); 1087-93). The reaction mechanism of isomerization,catalyzed by the Idi protein of E. coli, has been characterized inmechanistic detail (de Ruyck et al., J Biol. Chem. 281:17864-17869(2006)). Isopentenyl diphosphate isomerase enzymes from Saccharomycescerevisiae, Bacillus subtilis and Haematococcus pluvialis have beenheterologously expressed in E. coli (Laupitz et al., Eur. J Biochem.271:2658-2669 (2004); Kajiwara et al., Biochem. J 324 (Pt 2):421-426(1997)).

Protein GenBank ID GI Number Organism Idi NP_417365.1 16130791Escherichia coli IDI1 NP_015208.1 6325140 Saccharomyces cerevisiae IdiBAC82424.1 34327946 Sulfolobus shibatae Idi AAC32209.1 3421423Haematococcus pluvialis Idi BAB32625.1 12862826 Bacillus subtilis

Butadiene Synthase (FIG. 3, Step H)

Butadiene synthase catalyzes the conversion of 2-butenyl-4-diphosphateto 1,3-butadiene. The enzymes described below naturally possess suchactivity or can be engineered to exhibit this activity. Isoprenesynthase naturally catalyzes the conversion of dimethylallyl diphosphateto isoprene, but can also catalyze the synthesis of 1,3-butadiene from2-butenyl-4-diphosphate. Isoprene synthases can be found in severalorganisms including Populus alba (Sasaki et al., FEBS Letters, 579 (11),2514-2518 (2005)), Pueraria montana (Lindberg et al., Metabolic Eng,12(1):70-79 (2010); Sharkey et al., Plant Physiol., 137(2):700-712(2005)), and Populus tremula×Populus alba (Miller et al., Planta,213(3):483-487 (2001)). Additional isoprene synthase enzymes aredescribed in (Chotani et al., WO/2010/031079, Systems Using Cell Culturefor Production of Isoprene; Cervin et al., US Patent Application20100003716, Isoprene Synthase Variants for Improved MicrobialProduction of Isoprene).

Protein GenBank ID GI Number Organism ispS BAD98243.1 63108310 Populusalba ispS AAQ84170.1 35187004 Pueraria montana ispS CAC35696.1 13539551Populus tremula × Populus alba

Erythrose-4-Phosphate Kinase (FIG. 3, Step I)

In Step I of the pathway, erythrose-4-phosphate is converted toerythrose by the erythrose-4-phosphate kinase. In industrialfermentative production of erythritol by yeasts, glucose was convertedto erythrose-4-phosphate through the pentose phosphate pathway anderythrose-4-phosphate was dephosphorylated and reduced to produceerythritol (Moon et al., Appl. Microbiol Biotechnol. 86:1017-1025(2010)). Thus, erythrose-4-phosphate kinase is present in many of theseerythritol-producing yeasts, including Trichosporonoides megachiliensisSN-G42(Sawada et al., J Biosci. Bioeng. 108:385-390 (2009)), Candidamagnolia (Kohl et al., Biotechnol. Lett. 25:2103-2105 (2003)), andTorula sp. (HAJNY et al., Appl. Microbiol 12:240-246 (1964); Oh et al.,J Ind. Microbiol Biotechnol. 26:248-252 (2001)). However, theerythrose-4-phosphate kinase genes were not identified yet. There aremany polyol phosphotransferases with wide substrate range that can beapplied to this step. An example is the triose kinase (EC 2.7.1.28)catalyzing the reversible conversion between glyceraldehydes andglyceraldehydes-3-phosphate, which are one carbon shorter comparing toStep I. Other examples include the xylulokinase (EC 2.7.1.17) orarabinokinase (EC 2.7.1.54) that catalyzes phosphorylation of 5 C polyolaldehyde. The following genes can be used for Step I conversion:

Protein GenBank ID GI Number Organism xylB P09099.1 139849 Escherichiacoli strain K12 xks1 P42826.2 1723736 Saccharomyces cerevisiae xylBP29444.1 267426 Klebsiella pneumoniae dak1 Q9HFC5 74624685Zygosaccharomyces rouxii

Erythrose Reductase (FIG. 3, Step J)

In Step J of the pathway, erythrose is converted to erythritol by theerythrose reductase. In industrial fermentative production of erythritolby yeasts, glucose was converted to erythrose-4-phosphate through thepentose phosphate pathway and erythrose-4-phosphate was dephosphorylatedand reduced to produce erythritol (Moon et al., supra, (2010)). Thus,erythrose reductase is present in many of these erythritol-producingyeasts, including Trichosporonoides megachiliensis SN-G42 (Sawada etal., supra, (2009)), Candida magnolia (Kohl et al., supra, (2003)), andTorula sp. (HAJNY et al., supra, (1964); Oh et al., supra, (2001)).Erythrose reductase was characterized and purified from Torula corallina(Lee et al., Biotechnol. Prog. 19:495-500 (2003); Lee et al., Appl.Environ. Microbiol 68:4534-4538 (2002)), Candida magnolia (Lee et al.,Appl. Environ. Microbiol 69:3710-3718 (2003)) and Trichosporonoidesmegachiliensis SN-(i42 (Sawada et al., supra, (2009)). Several erythrosereductase genes were cloned and can be applied to Step J. The followinggenes can be used for Step J conversion:

Protein GenBank ID GI Number Organism alr ACT78580.1 254679867 Candidamagnoliae er1 BAD90687.1 60458781 Trichosporonoides megachiliensis er2BAD90688.1 60458783 Trichosporonoides megachiliensis er3 BAD90689.160458785 Trichosporonoides megachiliensis

Erythritol Kinase (FIG. 3, Step K)

In Step K of the pathway, erythritol is converted toerythritol-4-phosphate by the erythritol kinase. Erythritol kinase (EC2.7.1.27) catalyzes the phosphorylation of erythritol. Erythritol kinasewas characterized in erythritol utilizing bacteria such as Brucellaabortus (Sperry et al., J. Bacteriol. 121:619-630 (1975)). The eryA geneof Brucella abortus has been functionally expressed in Escherichia coliand the resultant EryA was shown to catalyze the ATP-dependentconversion of erythritol to erythritol-4-phosphate (Lillo et al.,Bioorg. Med. Chem. Lett. 13:737-739 (2003)). The following genes can beused for Step K conversion:

Protein GenBank ID GI Number Organism eryA Q8YCU8 81850596 Brucellamelitensis eriA Q92NH0 81774560 Sinorhizobium meliloti eryAYP_001108625.1 134102964 Saccharopolyspora erythraea NRRL 2338

Malonyl-CoA:Acetyl-CoA Acyltransferase (FIG. 4, Step A)

In Step A of the pathway described in FIG. 4, malonyl-CoA and acetyl-CoAare condensed to form 3-oxoglutaryl-CoA by malonyl-CoA:acetyl-CoA acyltransferase, a beta-keothiolase. Although no enzyme with activity onmalonyl-CoA has been reported to date, a good candidate for thistransformation is beta-ketoadipyl-CoA thiolase (EC 2.3.1.174), alsocalled 3-oxoadipyl-CoA thiolase that converts beta-ketoadipyl-CoA tosuccinyl-CoA and acetyl-CoA, and is a key enzyme of the beta-ketoadipatepathway for aromatic compound degradation. The enzyme is widespread insoil bacteria and fungi including Pseudomonas putida (Harwood et al., J.Bacteriol. 176:6479-6488 (1994)) and Acinetobacter calcoaceticus (Dotenet al., J. Bacteriol. 169:3168-3174 (1987)). The gene products encodedby pcaF in Pseudomonas strain B13 (Kaschabek et al., J. Bacteriol.184:207-215 (2002)), phaD in Pseudomonas putida U (Olivera et al.,supra, (1998)), paaE in Pseudomonas fluorescens ST (Di Gennaro et al.,Arch Microbiol. 88:117-125 (2007)), and paaJ from E. coli (Nogales etal., Microbiology, 153:357-365 (2007)) also catalyze thistransformation. Several beta-ketothiolases exhibit significant andselective activities in the oxoadipyl-CoA forming direction includingbkt from Pseudomonas putida, pcaF and bkt from Pseudomonas aeruginosaPAO1, bkt from Burkholderia ambifaria AMMD, paaJ from E. coli, and phaDfrom P. putida. These enzymes can also be employed for the synthesis of3-oxoglutaryl-CoA, a compound structurally similar to 3-oxoadipyl-CoA.

Protein GenBank ID GI Number Organism paaJ NP_415915.1 16129358Escherichia coli pcaF AAL02407 17736947 Pseudomonas knackmussii (B13)phaD AAC24332.1 3253200 Pseudomonas putida pcaF AAA85138.1 506695Pseudomonas putida pcaF AAC37148.1 141777 Acinetobacter calcoaceticuspaaE ABF82237.1 106636097 Pseudomonas fluorescens bkt YP_777652.1115360515 Burkholderia ambifaria AMMD bkt AAG06977.1 9949744 Pseudomonasaeruginosa PAO1 pcaF AAG03617.1 9946065 Pseudomonas aeruginosa PAO1

Another relevant beta-ketothiolase is oxopimeloyl-CoA:glutaryl-CoAacyltransferase (EC 2.3.1.16) that combines glutaryl-CoA and acetyl-CoAto form 3-oxopimeloyl-CoA. An enzyme catalyzing this transformation isfound in Ralstonia eutropha (formerly known as Alcaligenes eutrophus),encoded by genes bktB and bktC (Slater et al., J. Bacteriol.180:1979-1987 (1998); Haywood et al., FEMS Microbiology Letters 52:91-96(1988)). The sequence of the BktB protein is known; however, thesequence of the BktC protein has not been reported. The pim operon ofRhodopseudomonas palustris also encodes a beta-ketothiolase, encoded bypima, predicted to catalyze this transformation in the degradativedirection during benzoyl-CoA degradation (Harrison et al., Microbiology151:727-736 (2005)). A beta-ketothiolase enzyme candidate in S.aciditrophicus was identified by sequence homology to bktB (43%identity, evalue=1e−93).

Protein GenBank ID GI Number Organism bktB YP_725948 11386745 Ralstoniaeutropha pimB CAE29156 39650633 Rhodopseudomonas palustris syn_02642YP_462685.1 85860483 Syntrophus aciditrophicus

Beta-ketothiolase enzymes catalyzing the formation ofbeta-ketovaleryl-CoA from acetyl-CoA and propionyl-CoA can also be ableto catalyze the formation of 3-oxoglutaryl-CoA. Zoogloea ramigerapossesses two ketothiolases that can form β-ketovaleryl-CoA frompropionyl-CoA and acetyl-CoA and R. eutropha has a β-oxidationketothiolase that is also capable of catalyzing this transformation(Slater et al., J. Bacteriol, 180:1979-1987 (1998)). The sequences ofthese genes or their translated proteins have not been reported, butseveral candidates in R. eutropha, Z. ramigera, or other organisms canbe identified based on sequence homology to bktB from R. eutropha. Theseinclude:

Protein GenBank ID GI Number Organism phaA YP_725941.1 113867452Ralstonia eutropha h16_A1713 YP_726205.1 113867716 Ralstonia eutrophapcaF YP_728366.1 116694155 Ralstonia eutropha h16_B1369 YP_840888.1116695312 Ralstonia eutropha h16_A0170 YP_724690.1 113866201 Ralstoniaeutropha h16_A0462 YP_724980.1 113866491 Ralstonia eutropha h16_A1528YP_726028.1 113867539 Ralstonia eutropha h16_B0381 YP_728545.1 116694334Ralstonia eutropha h16_B0662 YP_728824.1 116694613 Ralstonia eutrophah16_B0759 YP_728921.1 116694710 Ralstonia eutropha h16_B0668 YP_728830.1116694619 Ralstonia eutropha h16_A1720 YP_726212.1 113867723 Ralstoniaeutropha h16_A1887 YP_726356.1 113867867 Ralstonia eutropha phbAP07097.4 135759 Zoogloea ramigera bktB YP_002005382.1 194289475Cupriavidus taiwanensis Rmet_1362 YP_583514.1 94310304 Ralstoniametallidurans Bphy_0975 YP_001857210.1 186475740 Burkholderia phymatum

Additional candidates include beta-ketothiolases that are known toconvert two molecules of acetyl-CoA into acetoacetyl-CoA (EC 2.1.3.9).Exemplary acetoacetyl-CoA thiolase enzymes include the gene products ofatoB from E. coli (Martin et al., supra, (2003)), thlA and thlB from C.acetobutylicum (Hanai et al., supra, (2007); Winzer et al., supra,(2000)), and ERG10 from S. cerevisiae (Hiser et al., supra, (1994)).

Protein GenBank ID GI Number Organism toB NP_416728 16130161 Escherichiacoli thlA NP_349476.1 15896127 Clostridium acetobutylicum thlBNP_149242.1 15004782 Clostridium acetobutylicum ERG10 NP_015297 6325229Saccharomyces cerevisiae

3-Oxoglutaryl-CoA Reductase (Ketone-Reducing) (FIG. 4, Step B)

This enzyme catalyzes the reduction of the 3-oxo group in3-oxoglutaryl-CoA to the 3-hydroxy group in Step B of the pathway shownin FIG. 4.

3-Oxoacyl-CoA dehydrogenase enzymes convert 3-oxoacyl-CoA molecules into3-hydroxyacyl-CoA molecules and are often involved in fatty acidbeta-oxidation or phenylacetate catabolism. For example, subunits of twofatty acid oxidation complexes in E. coli, encoded by fadB and fadJ,function as 3-hydroxyacyl-CoA dehydrogenases (Binstock et al., MethodsEnzymol. 71 Pt C:403-411 (1981)). Furthermore, the gene products encodedby phaC in Pseudomonas putida U (Olivera et al., supra, (1998)) and paaCin Pseudomonas fluorescens ST (Di et al., supra, (2007)) catalyze thereversible oxidation of 3-hydroxyadipyl-CoA to form 3-oxoadipyl-CoA,during the catabolism of phenylacetate or styrene. In addition, giventhe proximity in E. coli of paaH to other genes in the phenylacetatedegradation operon (Nogales et al., supra, (2007)) and the fact thatpaaH mutants cannot grow on phenylacetate (Ismail et al., supra,(2003)), it is expected that the E. coli paaH gene encodes a3-hydroxyacyl-CoA dehydrogenase.

Protein GenBank ID GI Number Organism fadB P21177.2 119811 Escherichiacoli fadJ P77399.1 3334437 Escherichia coli paaH NP_415913.1 16129356Escherichia coli phaC NP_745425.1 26990000 Pseudomonas putida paaCABF82235.1 106636095 Pseudomonas fluorescens

3-Hydroxybutyryl-CoA dehydrogenase, also called acetoacetyl-CoAreductase, catalyzes the reversible NAD(P)H-dependent conversion ofacetoacetyl-CoA to 3-hydroxybutyryl-CoA. This enzyme participates in theacetyl-CoA fermentation pathway to butyrate in several species ofClostridia and has been studied in detail (Jones and Woods, supra,(1986)). Enzyme candidates include hbd from C. acetobutylicum (Boyntonet al., J. Bacteriol. 178:3015-3024 (1996)), hbd from C. beijerinckii(Colby et al., Appl Environ. Microbiol 58:3297-3302 (1992)), and anumber of similar enzymes from Metallosphaera sedula (Berg et al.,supra, (2007)). The enzyme from Clostridium acetobutylicum, encoded byhbd, has been cloned and functionally expressed in E. coli (Younglesonet al., supra, (1989)). Yet other genes demonstrated to reduceacetoacetyl-CoA to 3-hydroxybutyryl-CoA are phbB from Zoogloea ramigera(Ploux et al., supra, (1988)) and phaB from Rhodobacter sphaeroides(Alber et al., supra, (2006)). The former gene is NADPH-dependent, itsnucleotide sequence has been determined (Peoples and Sinskey, supra,(1989)) and the gene has been expressed in E. coli. Additional genesinclude hbd1 (C-terminal domain) and hbd2 (N-terminal domain) inClostridium kluyveri (Hillmer and Gottschalk, Biochim. Biophys. Acta3334:12-23 (1974)) and HSD17B10 in Bos taurus (WAKIL et al., supra,(1954)).

Protein GenBank ID GI Number Organism hbd NP_349314.1 15895965Clostridium acetobutylicum hbd AAM14586.1 20162442 Clostridiumbeijerinckii Msed_1423 YP_001191505 146304189 Metallosphaera sedulaMsed_0399 YP_001190500 146303184 Metallosphaera sedula Msed_0389YP_001190490 146303174 Metallosphaera sedula Msed_1993 YP_001192057146304741 Metallosphaera sedula hbd2 EDK34807.1 146348271 Clostridiumkluyveri hbd1 EDK32512.1 146345976 Clostridium kluyveri HSD17B10O02691.3 3183024 Bos taurus phaB YP_353825.1 77464321 Rhodobactersphaeroides phbB P23238.1 130017 Zoogloea ramigera

3-Hydroxyglutaryl-CoA Reductase (Aldehyde Forming) (FIG. 4, Step C)

3-hydroxyglutaryl-CoA reductase reduces 3-hydroxyglutaryl-CoA to3-hydroxy-5-oxopentanoate. Several acyl-CoA dehydrogenases reduce anacyl-CoA to its corresponding aldehyde (EC 1.2.1). Exemplary genes thatencode such enzymes include the Acinetobacter calcoaceticus acy1encoding a fatty acyl-CoA reductase (Reiser and Somerville, supra,(1997)), the Acinetobacter sp. M-1 fatty acyl-CoA reductase (Ishige etal., supra, (2002)), and a CoA- and NADP-dependent succinatesemialdehyde dehydrogenase encoded by the sucD gene in Clostridiumkluyveri (Sohling and Gottschalk, supra, (1996); Sohling and Gottschalk,supra, (1996)). SucD of P. gingivalis is another succinate semialdehydedehydrogenase (Takahashi et al., supra, (2000)). The enzyme acylatingacetaldehyde dehydrogenase in Pseudomonas sp, encoded by bphG, is yetanother as it has been demonstrated to oxidize and acylate acetaldehyde,propionaldehyde, butyraldehyde, isobutyraldehyde and formaldehyde(Powlowski et al., supra, (1993)). In addition to reducing acetyl-CoA toethanol, the enzyme encoded by adhE in Leuconostoc mesenteroides hasbeen shown to oxidize the branched chain compound isobutyraldehyde toisobutyryl-CoA (Koo et al., Biotechnol Lett. 27:505-510 (2005)).Butyraldehyde dehydrogenase catalyzes a similar reaction, conversion ofbutyryl-CoA to butyraldehyde, in solventogenic organisms such asClostridium saccharoperbutylacetonicum (Kosaka et al., Biosci.Biotechnol Biochem. 71:58-68 (2007)).

Protein GenBank ID GI Number Organism acr1 YP_047869.1 50086359Acinetobacter calcoaceticus acr1 AAC45217 1684886 Acinetobacter baylyiacr1 BAB85476.1 18857901 Acinetobacter sp. Strain M-1 sucD P38947.1172046062 Clostridium kluyveri sucD NP_904963.1 34540484 Porphyromonasgingivalis bphG BAA03892.1 425213 Pseudomonas sp adhE AAV66076.155818563 Leuconostoc mesenteroides bld AAP42563.1 31075383 Clostridiumsaccharoperbutylacetonicum

An additional enzyme type that converts an acyl-CoA to its correspondingaldehyde is malonyl-CoA reductase which transforms malonyl-CoA tomalonic semialdehyde. Malonyl-CoA reductase is a key enzyme inautotrophic carbon fixation via the 3-hydroxypropionate cycle inthermoacidophilic archael bacteria (Berg et al., supra, (2007b); Thauer,supra, (2007)). The enzyme utilizes NADPH as a cofactor and has beencharacterized in Metallosphaera and Sulfolobus spp (Alber et al., supra,(2006); Hugler et al., supra, (2002)). The enzyme is encoded byMsed_(—)0709 in Metallosphaera sedula (Alber et al., supra, (2006); Berget al., supra, (2007b)). A gene encoding a malonyl-CoA reductase fromSulfolobus tokodaii was cloned and heterologously expressed in E. coli(Alber et al., supra, (2006)). This enzyme has also been shown tocatalyze the conversion of methylmalonyl-CoA to its correspondingaldehyde (WO/2007/141208). Although the aldehyde dehydrogenasefunctionality of these enzymes is similar to the bifunctionaldehydrogenase from Chloroflexus aurantiacus, there is little sequencesimilarity. Both malonyl-CoA reductase enzyme candidates have highsequence similarity to aspartate-semialdehyde dehydrogenase, an enzymecatalyzing the reduction and concurrent dephosphorylation ofaspartyl-4-phosphate to aspartate semialdehyde. Additional genecandidates can be found by sequence homology to proteins in otherorganisms including Sulfolobus solfataricus and Sulfolobusacidocaldarius. Yet another acyl-CoA reductase (aldehyde forming)candidate is the ald gene from Clostridium beijerinckii (Toth et al.,Appl Environ. Microbiol 65:4973-4980 (1999)). This enzyme has beenreported to reduce acetyl-CoA and butyryl-CoA to their correspondingaldehydes. This gene is very similar to eutE that encodes acetaldehydedehydrogenase of Salmonella typhimurium and E. coli (Toth et al., supra,(1999)).

Protein GenBank ID GI Number Organism MSED_0709 YP_001190808.1 146303492Metallosphaera sedula mcr NP_378167.1 15922498 Sulfolobus tokodaii asd-2NP_343563.1 15898958 Sulfolobus solfataricus Saci_2370 YP_256941.170608071 Sulfolobus acidocaldarius Ald AAT66436 9473535 Clostridiumbeijerinckii eutE AAA80209 687645 Salmonella typhimurium eutE P774452498347 Escherichia coli

3-Hydroxy-5-Oxopentanoate Reductase (FIG. 4, Step D)

This enzyme reduces the terminal aldehyde group in3-hydroxy-5-oxopentanote to the alcohol group. Exemplary genes encodingenzymes that catalyze the conversion of an aldehyde to alcohol (i.e.,alcohol dehydrogenase or equivalently aldehyde reductase, 1.1.1.a)include alrA encoding a medium-chain alcohol dehydrogenase for C2-C14(Tani et al., supra, (2000)), ADH2 from Saccharomyces cerevisiae (Atsumiet al., supra, (2008)), yqhD from E. coli which has preference formolecules longer than C(3) (Sulzenbacher et al., supra, (2004)), and bdhI and bdh II from C. acetobutylicum which converts butyryaldehyde intobutanol (Walter et al., supra, (1992)). The gene product of yqhDcatalyzes the reduction of acetaldehyde, malondialdehyde,propionaldehyde, butyraldehyde, and acrolein using NADPH as the cofactor(Perez et al., 283:7346-7353 (2008); Perez et al., J Biol. Chem.283:7346-7353 (2008)). The adhA gene product from Zymomonas mobilis hasbeen demonstrated to have activity on a number of aldehydes includingformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, and acrolein(Kinoshita et al., Appl Microbiol Biotechnol 22:249-254 (1985)).

Protein GenBank ID GI Number Organism alrA BAB12273.1 9967138Acinetobacter sp. Strain M-1 ADH2 NP_014032.1 6323961 Saccharomycescerevisiae yqhD NP_417484.1 16130909 Escherichia coli bdh I NP_349892.115896543 Clostridium acetobutylicum bdh II NP_349891.1 15896542Clostridium acetobutylicum adhA YP_162971.1 56552132 Zymomonas mobilis

Enzymes exhibiting 4-hydroxybutyrate dehydrogenase activity (EC1.1.1.61) also fall into this category. Such enzymes have beencharacterized in Ralstonia eutropha (Bravo et al., supra, (2004)),Clostridium kluyveri (Wolff and Kenealy, supra, (1995)) and Arabidopsisthaliana (Breitkreuz et al., supra, (2003)). The A. thaliana enzyme wascloned and characterized in yeast [12882961]. Yet another gene is thealcohol dehydrogenase adhI from Geobacillus thermoglucosidasius (Jeon etal., J Biotechnol 135:127-133 (2008)).

Protein GenBank ID GI Number Organism 4hbd YP_726053.1 113867564Ralstonia eutropha H16 4hbd EDK35022.1 146348486 Clostridium kluyveri4hbd Q94B07 75249805 Arabidopsis thaliana adhI AAR91477.1 40795502Geobacillus thermoglucosidasius

Another exemplary enzyme is 3-hydroxyisobutyrate dehydrogenase (EC1.1.1.31) which catalyzes the reversible oxidation of3-hydroxyisobutyrate to methylmalonate semialdehyde. This enzymeparticipates in valine, leucine and isoleucine degradation and has beenidentified in bacteria, eukaryotes, and mammals. The enzyme encoded byP84067 from Thermus thermophilus HB8 has been structurally characterized(Lokanath et al., J Mol Biol 352:905-17 (2005)). The reversibility ofthe huma 3-hydroxyisobutyrate dehydrogenase was demonstrated usingisotopically-labeled substrate (Manning et al., Biochem J 231:481-4(1985)). Additional genes encoding this enzyme include 3hidh in Homosapiens (Hawes et al., Methods Enzymol 324:218-228 (2000)) andOryctolagus cuniculus (Hawes et al., supra, (2000); Chowdhury et al.,Biosci. Biotechnol Biochem. 60:2043-2047 (1996)), mmsb in Pseudomonasaeruginosa, and dhat in Pseudomonas putida (Aberhart et al., J. Chem.Soc.[Perkin I] 6:1404-1406 (1979); Chowdhury et al., supra, (1996);Chowdhury et al., Biosci. Biotechnol Biochem. 67:438-441 (2003)).

Protein GenBank ID GI Number Organism P84067 P84067 75345323 Thermusthermophilus mmsb P28811.1 127211 Pseudomonas aeruginosa dhat Q59477.12842618 Pseudomonas putida 3hidh P31937.2 12643395 Homo sapiens 3hidhP32185.1 416872 Oryctolagus cuniculus

The conversion of malonic semialdehyde to 3-HP can also be accomplishedby two other enzymes: NADH-dependent 3-hydroxypropionate dehydrogenaseand NADPH-dependent malonate semialdehyde reductase. An NADH-dependent3-hydroxypropionate dehydrogenase is thought to participate inbeta-alanine biosynthesis pathways from propionate in bacteria andplants (Rathinasabapathi B., Journal of Plant Pathology 159:671-674(2002); Stadtman, J. Am. Chem. Soc. 77:5765-5766 (1955)). This enzymehas not been associated with a gene in any organism to date.NADPH-dependent malonate semialdehyde reductase catalyzes the reversereaction in autotrophic CO2-fixing bacteria. Although the enzymeactivity has been detected in Metallosphaera sedula, the identity of thegene is not known (Alber et al., supra, (2006)).

3,5-Dihydroxypentanoate Kinase (FIG. 4, Step E)

This enzyme phosphorylates 3,5-dihydroxypentanotae in FIG. 4 (Step E) toform 3-hydroxy-5-phosphonatooxypentanoate (3H5PP). This transformationcan be catalyzed by enzymes in the EC class 2.7.1 that enable theATP-dependent transfer of a phosphate group to an alcohol.

A good candidate for this step is mevalonate kinase (EC 2.7.1.36) thatphosphorylates the terminal hydroxyl group of the methyl analog,mevalonate, of 3,5-dihydroxypentanote. Some gene candidates for thisstep are erg12 from S. cerevisiae, mvk from Methanocaldococcusjannaschi, MVK from Homo sapeins, and mvk from Arabidopsis thaliana col.

Protein GenBank ID GI Number Organism erg12 CAA39359.1 3684Sachharomyces cerevisiae mvk Q58487.1 2497517 Methanocaldococcusjannaschii mvk AAH16140.1 16359371 Homo sapiens M\mvk NP_851084.130690651 Arabidopsis thaliana

Glycerol kinase also phosphorylates the terminal hydroxyl group inglycerol to form glycerol-3-phosphate. This reaction occurs in severalspecies, including Escherichia coli, Saccharomyces cerevisiae, andThermotoga maritima. The E. coli glycerol kinase has been shown toaccept alternate substrates such as dihydroxyacetone and glyceraldehyde(Hayashi and Lin, supra, (1967)). T, maritime has two glycerol kinases(Nelson et al., supra, (1999)). Glycerol kinases have been shown to havea wide range of substrate specificity. Crans and Whiteside studiedglycerol kinases from four different organisms (Escherichia coli, S.cerevisiae, Bacillus stearothermophilus, and Candida mycoderma) (Cransand Whitesides, supra, (2010); Nelson et al., supra, (1999)). Theystudied 66 different analogs of glycerol and concluded that the enzymecould accept a range of substituents in place of one terminal hydroxylgroup and that the hydrogen atom at C2 could be replaced by a methylgroup. Interestingly, the kinetic constants of the enzyme from all fourorganisms were very similar. The gene candidates are:

Protein GenBank ID GI Number Organism glpK AP_003883.1 89110103Escherichia coli K12 glpK1 NP_228760.1 15642775 Thermotoga maritime MSB8glpK2 NP_229230.1 15642775 Thermotoga maritime MSB8 Gut1 NP_011831.182795252 Saccharomyces cerevisiae

Homoserine kinase is another possible candidate that can lead to thephosphorylation of 3,5-dihydroxypentanoate. This enzyme is also presentin a number of organisms including E. coli, Streptomyces sp, and S.cerevisiae. Homoserine kinase from E. coli has been shown to haveactivity on numerous substrates, including, L-2-amino,1,4-butanediol,aspartate semialdehyde, and 2-amino-5-hydroxyvalerate (Huo and Viola,supra, (1996); Huo and Viola, supra, (1996)). This enzyme can act onsubstrates where the carboxyl group at the alpha position has beenreplaced by an ester or by a hydroxymethyl group. The gene candidatesare:

Protein GenBank ID GI Number Organism thrB BAB96580.2 85674277Escherichia coli K12 SACT1DRAFT_4809 ZP_06280784.1 282871792Streptomyces sp. ACT-1 Thr1 AAA35154.1 172978 Saccharomyces serevisiae

3H5PP Kinase (FIG. 4, Step F)

Phosphorylation of 3H5PP to 3H5PDP is catalyzed by 3H5PP kinase (FIG. 4,Step F). Phosphomevalonate kinase (EC 2.7.4.2) catalyzes the analogoustransformation in the mevalonate pathway. This enzyme is encoded by erg8in Saccharomyces cerevisiae (Tsay et al., Mol. Cell Biol. 11:620-631(1991)) and mvaK2 in Streptococcus pneumoniae, Staphylococcus aureus andEnterococcus faecalis (Doun et al., Protein Sci. 14:1134-1139 (2005);Wilding et al., J. Bacteriol. 182:4319-4327 (2000)). The Streptococcuspneumoniae and Enterococcus faecalis enzymes were cloned andcharacterized in E. coli (Pilloff et al., J. Biol. Chem. 278:4510-4515(2003); Doun et al., Protein Sci. 14:1134-1139 (2005)).

Protein GenBank ID GI Number Organism Erg8 AAA34596.1 171479Saccharomyces cerevisiae mvaK2 AAG02426.1 9937366 Staphylococcus aureusmvaK2 AAG02457.1 9937409 Streptococcus pneumoniae mvaK2 AAG02442.19937388 Enterococcus faecalis

3H5PDP Decarboxylase (FIG. 4, Step G)

Butenyl 4-diphosphate is formed from the ATP-dependent decarboxylationof 3H5PDP by 3H5PDP decarboxylase (FIG. 4, Step G). Although an enzymewith this activity has not been characterized to date a similar reactionis catalyzed by mevalonate diphosphate decarboxylase (EC 4.1.1.33), anenzyme participating in the mevalonate pathway for isoprenoidbiosynthesis. This reaction is catalyzed by MVD1 in Saccharomycescerevisiae, MVD in Homo sapiens and MDD in Staphylococcus aureus andTrypsonoma brucei (Toth et al., J Biol. Chem. 271:7895-7898 (1996);Byres et al., J Mol. Biol. 371:540-553 (2007)).

Protein GenBank ID GI Number Organism MVD1 P32377.2 1706682Saccharomyces cerevisiae MVD NP_002452.1 4505289 Homo sapiens MDDABQ48418.1 147740120 Staphylococcus aureus MDD EAN78728.1 70833224Trypsonoma brucei

Butenyl 4-Diphosphate Isomerase (FIG. 4, Step H)

Butenyl 4-diphosphate isomerase catalyzes the reversible interconversionof 2-butenyl-4-diphosphate and butenyl-4-diphosphate. The followingenzymes can naturally possess this activity or can be engineered toexhibit this activity. Useful genes include those that encode enzymesthat interconvert isopenenyl diphosphate and dimethylallyl diphosphate.These include isopentenyl diphosphate isomerase enzymes from Escherichiacoli (Rodríguez-Concepción et al., FEBS Lett, 473(3):328-332),Saccharomyces cerevisiae (Anderson et al., J Biol Chem, 1989, 264(32);19169-75), and Sulfolobus shibatae (Yamashita et al, Eur J Biochem,2004, 271(6); 1087-93). The reaction mechanism of isomerization,catalyzed by the Idi protein of E. coli, has been characterized inmechanistic detail (de Ruyck et al., J Biol. Chem. 281:17864-17869(2006)). Isopentenyl diphosphate isomerase enzymes from Saccharomycescerevisiae, Bacillus subtilis and Haematococcus pluvialis have beenheterologously expressed in E. coli (Laupitz et al., Eur. J Biochem.271:2658-2669 (2004); Kajiwara et al., Biochem. J 324 (Pt 2):421-426(1997)).

Protein GenBank ID GI Number Organism Idi NP_417365.1 16130791Escherichia coli IDI1 NP_015208.1 6325140 Saccharomyces cerevisiae IdiBAC82424.1 34327946 Sulfolobus shibatae Idi AAC32209.1 3421423Haematococcus pluvialis Idi BAB32625.1 12862826 Bacillus subtilis

Butadiene Synthase (FIG. 4, Step I)

Butadiene synthase catalyzes the conversion of 2-butenyl-4-diphosphateto 1,3-butadiene. The enzymes described below naturally possess suchactivity or can be engineered to exhibit this activity. Isoprenesynthase naturally catalyzes the conversion of dimethylallyl diphosphateto isoprene, but can also catalyze the synthesis of 1,3-butadiene from2-butenyl-4-diphosphate. Isoprene synthases can be found in severalorganisms including Populus alba (Sasaki et al., FEBS Letters, 2005, 579(11), 2514-2518), Pueraria montana (Lindberg et al., Metabolic Eng,12(1):70-79 (2010); Sharkey et al., Plant Physiol., 137(2):700-712(2005)), and Populus tremula×Populus alba (Miller et al., Planta,213(3):483-487 (2001)). Additional isoprene synthase enzymes aredescribed in (Chotani et al., WO/2010/031079, Systems Using Cell Culturefor Production of Isoprene; Cervin et al., US Patent Application20100003716, Isoprene Synthase Variants for Improved MicrobialProduction of Isoprene).

Protein GenBank ID GI Number Organism ispS BAD98243.1 63108310 Populusalba ispS AAQ84170.1 35187004 Pueraria montana ispS CAC35696.1 13539551Populus tremula × Populus alba

3-Hydroxyglutaryl-CoA Reductase (Alcohol Forming) (FIG. 4, Step J)

This step catalyzes the reduction of the acyl-CoA group in3-hydroxyglutaryl-CoA to the alcohol group. Exemplary bifunctionaloxidoreductases that convert an acyl-CoA to alcohol include those thattransform substrates such as acetyl-CoA to ethanol (e.g., adhE from E.coli (Kessler et al., supra, (1991)) and butyryl-CoA to butanol (e.g.adhE2 from C. acetobutylicum (Fontaine et al., supra, (2002)). Inaddition to reducing acetyl-CoA to ethanol, the enzyme encoded by adhEin Leuconostoc mesenteroides has been shown to oxide the branched chaincompound isobutyraldehyde to isobutyryl-CoA (Kazahaya et al., supra,(1972); Koo et al., supra, (2005)).

Another exemplary enzyme can convert malonyl-CoA to 3-HP. AnNADPH-dependent enzyme with this activity has characterized inChloroflexus aurantiacus where it participates in the3-hydroxypropionate cycle (Hugler et al., supra, (2002); Strauss andFuchs, supra, (1993)). This enzyme, with a mass of 300 kDa, is highlysubstrate-specific and shows little sequence similarity to other knownoxidoreductases (Hugler et al., supra, (2002)). No enzymes in otherorganisms have been shown to catalyze this specific reaction; howeverthere is bioinformatic evidence that other organisms can have similarpathways (Klatt et al., supra, (2007)). Enzyme candidates in otherorganisms including Roseiflexus castenholzii, Erythrobacter sp. NAP1 andmarine gamma proteobacterium HTCC2080 can be inferred by sequencesimilarity.

Protein GenBank ID GI Number Organism adhE NP_415757.1 16129202Escherichia coli adhE2 AAK09379.1 12958626 Clostridium acetobutylicumadhE AAV66076.1 55818563 Leuconostoc mesenteroides mcr AAS20429.142561982 Chloroflexus aurantiacus Rcas_2929 YP_001433009.1 156742880Roseiflexus castenholzii NAP1_02720 ZP_01039179.1 85708113 Erythrobactersp. NAP1 MGP2080_00535 ZP_01626393.1 119504313 marine gammaproteobacterium HTCC2080

Longer chain acyl-CoA molecules can be reduced to their correspondingalcohols by enzymes such as the jojoba (Simmondsia chinensis) FAR whichencodes an alcohol-forming fatty acyl-CoA reductase. Its overexpressionin E. coli resulted in FAR activity and the accumulation of fattyalcohol (Metz et al., Plant Physiology 122:635-644 (2000)).

Protein GenBank ID GI Number Organism FAR AAD38039.1 5020215 Simmondsiachinensis

Another candidate for catalyzing this step is3-hydroxy-3-methylglutaryl-CoA reductase (or HMG-CoA reductase). Thisenzyme reduces the CoA group in 3-hydroxy-3-methylglutaryl-CoA to analcohol forming mevalonate. Gene candidates for this step include:

Protein GenBank ID GI Number Organism HMG1 CAA86503.1 587536Saccharomyces cerevisiae HMG2 NP_013555 6323483 Saccharomyces cerevisiaeHMG1 CAA70691.1 1694976 Arabidopsis thaliana hmgA AAC45370.1 2130564Sulfolobus solfataricus

The hmgA gene of Sulfolobus solfataricus, encoding3-hydroxy-3-methylglutaryl-CoA reductase, has been cloned, sequenced,and expressed in E. coli (Bochar et al., J Bacteriol. 179:3632-3638(1997)). S. cerevisiae also has two HMG-CoA reductases in it (Basson etal., Proc. Natl. Acad. Sci. U.S.A 83:5563-5567 (1986)). The gene hasalso been isolated from Arabidopsis thaliana and has been shown tocomplement the HMG-COA reductase activity in S. cerevisiae (Learned etal., Proc. Natl. Acad. Sci. U.S.A 86:2779-2783 (1989)).

3-Oxoglutaryl-CoA Reductase (Aldehyde Forming) (FIG. 4, Step K)

Several acyl-CoA dehydrogenases are capable of reducing an acyl-CoA toits corresponding aldehyde. Thus they can naturally reduce3-oxoglutaryl-CoA to 3,5-dioxopentanoate or can be engineered to do so.Exemplary genes that encode such enzymes were discussed in FIG. 4, StepC.

3,5-Dioxopentanoate Reductase (Ketone Reducing) (FIG. 4, Step L)

There exist several exemplary alcohol dehydrogenases that convert aketone to a hydroxyl functional group. Two such enzymes from E. coli areencoded by malate dehydrogenase (mdh) and lactate dehydrogenase (ldhA).In addition, lactate dehydrogenase from Ralstonia eutropha has beenshown to demonstrate high activities on 2-ketoacids of various chainlengths including lactate, 2-oxobutyrate, 2-oxopentanoate and2-oxoglutarate (Steinbuchel et al., Eur. J. Biochem. 130:329-334(1983)). Conversion of alpha-ketoadipate into alpha-hydroxyadipate canbe catalyzed by 2-ketoadipate reductase, an enzyme reported to be foundin rat and in human placenta (Suda et al., Arch. Biochem. Biophys.176:610-620 (1976); Suda et al., Biochem. Biophys. Res. Commun.77:586-591 (1977)). An additional candidate for this step is themitochondrial 3-hydroxybutyrate dehydrogenase (bdh) from the human heartwhich has been cloned and characterized (Marks et al., J. Biol. Chem.267:15459-15463 (1992)). This enzyme is a dehydrogenase that operates ona 3-hydroxyacid. Another exemplary alcohol dehydrogenase convertsacetone to isopropanol as was shown in C. beijerinckii (Ismaiel et al.,J. Bacteriol. 175:5097-5105 (1993)) and T. brockii (Lamed et al.,Biochem. J. 195:183-190 (1981); Peretz et al., Biochemistry.28:6549-6555 (1989)). Methyl ethyl ketone reductase, or alternatively,2-butanol dehydrogenase, catalyzes the reduction of MEK to form2-butanol. Exemplary enzymes can be found in Rhodococcus ruber (Kosjeket al., Biotechnol Bioeng. 86:55-62 (2004)) and Pyrococcus furiosus (vander et al., Eur. J. Biochem. 268:3062-3068 (2001)).

Protein GenBank ID GI Number Organism mdh AAC76268.1 1789632 Escherichiacoli ldhA NP_415898.1 16129341 Escherichia coli ldh YP_725182.1113866693 Ralstonia eutropha bdh AAA58352.1 177198 Homo sapiens adhAAA23199.2 60592974 Clostridium beijerinckii NRRL B593 adh P14941.1113443 Thermoanaerobacter brockii HTD4 adhA AAC25556 3288810 Pyrococcusfuriosus adh-A CAD36475 21615553 Rhodococcus ruber

A number of organisms can catalyze the reduction of 4-hydroxy-2-butanoneto 1,3-butanediol, including those belonging to the genus Bacillus,Brevibacterium, Candida, and Klebsiella among others, as described byMatsuyama et al. U.S. Pat. No. 5,413,922. A mutated Rhodococcusphenylacetaldehyde reductase (Sar268) and a Leifonia alcoholdehydrogenase have also been shown to catalyze this transformation athigh yields (Itoh et al., Appl. Microbiol. Biotechnol. 75(6):1249-1256).

Homoserine dehydrogenase (EC 1.1.1.13) catalyzes the NAD(P)H-dependentreduction of aspartate semialdehyde to homoserine. In many organisms,including E. coli, homoserine dehydrogenase is a bifunctional enzymethat also catalyzes the ATP-dependent conversion of aspartate toaspartyl-4-phosphate (Starnes et al., Biochemistry 11:677-687 (1972)).The functional domains are catalytically independent and connected by alinker region (Sibilli et al., J Biol Chem 256:10228-10230 (1981)) andboth domains are subject to allosteric inhibition by threonine. Thehomoserine dehydrogenase domain of the E. coli enzyme, encoded by thrA,was separated from the aspartate kinase domain, characterized, and foundto exhibit high catalytic activity and reduced inhibition by threonine(James et al., Biochemistry 41:3720-3725 (2002)). This can be applied toother bifunctional threonine kinases including, for example, hom1 ofLactobacillus plantarum (Cahyanto et al., Microbiology 152:105-112(2006)) and Arabidopsis thaliana. The monofunctional homoserinedehydrogenases encoded by hom6 in S. cerevisiae (Jacques et al., BiochimBiophys Acta 1544:28-41 (2001)) and hom2 in Lactobacillus plantarum(Cahyanto et al., supra, (2006)) have been functionally expressed andcharacterized in E. coli.

Protein GenBank ID GI number Organism thrA AAC73113.1 1786183Escherichia coli K12 akthr2 O81852 75100442 Arabidopsis thaliana hom6CAA89671 1015880 Saccharomyces cerevisiae hom1 CAD64819 28271914Lactobacillus plantarum hom2 CAD63186 28270285 Lactobacillus plantarum

3,5-Dioxopentanoate Reductase (Aldehyde Reducing) (FIG. 4, Step M)

Several aldehyde reducing reductases are capable of reducing an aldehydeto its corresponding alcohol. Thus they can naturally reduce3,5-dioxopentanoate to 5-hydroxy-3-oxopentanoate or can be engineered todo so. Exemplary genes that encode such enzymes were discussed in FIG.4, Step D.

5-Hydroxy-3-Oxopentanoate Reductase (FIG. 4, Step N)

Several ketone reducing reductases are capable of reducing a ketone toits corresponding hydroxyl group. Thus they can naturally reduce5-hydroxy-3-oxopentanoate to 3,5-dihydroxypentanoate or can beengineered to do so. Exemplary genes that encode such enzymes werediscussed in FIG. 4, Step L.

3-Oxo-Glutaryl-CoA Reductase (CoA Reducing and Alcohol Forming) (FIG. 4,Step O)

3-oxo-glutaryl-CoA reductase (CoA reducing and alcohol forming) enzymescatalyze the 2 reduction steps required to form5-hydroxy-3-oxopentanoate from 3-oxo-glutaryl-CoA. Exemplary 2-stepoxidoreductases that convert an acyl-CoA to an alcohol were provided forFIG. 4, Step J. Such enzymes can naturally convert 3-oxo-glutaryl-CoA to5-hydroxy-3-oxopentanoate or can be engineered to do so.

Example II Chemical Production of Butadiene from Crotyl Alcohol

In a typical process for converting crotyl alcohol into butadiene,crotyl alcohol is passed, either neat or in a solvent and either inpresence or absence of steam, over a solid inorganic, organic ormetal-containing dehydration catalyst heated to temperatures in therange 40-400° C. inside of the reaction vessel or tube, leading toelimination of water and release of butadiene as a gas, which iscondensed (butadiene bp=−4.4° C.) and collected in a reservoir forfurther processing, storage, or use. Typical catalysts can includebismuth molybdate, phosphate-phosphoric acid, cerium oxide, kaolin-ironoxide, kaolin-phosphoric acid, silica-alumina, and alumina. Typicalprocess throughputs are in the range of 0.1-20,000 kg/h. Typicalsolvents are toluene, heptane, octane, ethylbenzene, and xylene.

Throughout this application various publications have been referenced.The disclosures of these publications in their entireties, includingGenBank and GI number publications, are hereby incorporated by referencein this application in order to more fully describe the state of the artto which this invention pertains. Although the invention has beendescribed with reference to the examples provided above, it should beunderstood that various modifications can be made without departing fromthe spirit of the invention.

1. A process for the production of butadiene comprising: (a) culturing by fermentation in a sufficient amount of nutrients and media a non-naturally occurring microbial organism that produces crotyl alcohol; and (b) converting crotyl alcohol produced by culturing said non-naturally occurring microbial organism to butadiene.
 2. The process of claim 1, wherein step (b) is performed by chemical dehydration in the presence of a catalyst.
 3. The process of claim 1, wherein said non-naturally occurring microbial organism comprises a crotyl alcohol pathway comprising at least one exogenous nucleic acid encoding a crotyl alcohol pathway enzyme expressed in a sufficient amount to produce crotyl alcohol, said crotyl alcohol pathway comprising an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehyde forming), a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase, or transferase, a crotonate reductase, a crotonyl-CoA reductase (alcohol forming), a glutaconyl-CoA decarboxylase, a glutaryl-CoA dehydrogenase, a 3-aminobutyryl-CoA deaminase, or a 4-hydroxybutyryl-CoA dehydratase.
 4. The process of claim 3, wherein said microbial organism comprises two, three or four exogenous nucleic acids each encoding a crotyl alcohol pathway enzyme. 5-6. (canceled)
 7. The process of claim 3, wherein said crotyl alcohol pathway comprises a pathway selected from the group consisting of: an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, and a crotonyl-CoA reductase (alcohol forming); an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase or transferase and a crotonate reductase; a glutaconyl-CoA decarboxylase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); a glutaconyl-CoA decarboxylase and a crotonyl-CoA reductase (alcohol forming); a glutaconyl-CoA decarboxylase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase, or transferase and a crotonate reductase; a glutaryl-CoA dehydrogenase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); a glutaryl-CoA dehydrogenase and a crotonyl-CoA reductase (alcohol forming); a glutaryl-CoA dehydrogenase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase, or transferase and a crotonate reductase; a 3-aminobutyryl-CoA deaminase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); a 3-aminobutyryl-CoA deaminase and a crotonyl-CoA reductase (alcohol forming); a 3-aminobutyryl-CoA deaminase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase or transferase and a crotonate reductase; a 4-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); a 4-hydroxybutyryl-CoA dehydratase and a crotonyl-CoA reductase (alcohol forming); and a 4-hydroxybutyryl-CoA dehydratase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase or transferase and a crotonate reductase. 8-21. (canceled)
 22. The process of claim 3, wherein said at least one exogenous nucleic acid is a heterologous nucleic acid.
 23. The process of claim 3, wherein said non-naturally occurring microbial organism is in a substantially anaerobic culture medium.
 24. A non-naturally occurring microbial organism comprising a crotyl alcohol pathway, said crotyl alcohol pathway comprising at least one exogenous nucleic acid encoding a crotyl alcohol pathway enzyme expressed in a sufficient amount to produce crotyl alcohol, said crotyl alcohol pathway comprising an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehyde forming), a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase, or transferase, a crotonate reductase, a crotonyl-CoA reductase (alcohol forming), a glutaconyl-CoA decarboxylase, a glutaryl-CoA dehydrogenase, a 3-aminobutyryl-CoA deaminase, or a 4-hydroxybutyryl-CoA dehydratase.
 25. The microbial organism of claim 24, wherein said microbial organism comprises two, three or four exogenous nucleic acids each encoding a crotyl alcohol pathway enzyme. 26-27. (canceled)
 28. The microbial organism of claim 24, wherein said crotyl alcohol pathway comprises a pathway selected from the group consisting of: an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, and a crotonyl-CoA reductase (alcohol forming); an acetyl-CoA:acetyl-CoA acyltransferase, an acetoacetyl-CoA reductase, a 3-hydroxybutyryl-CoA dehydratase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase or transferase and a crotonate reductase; a glutaconyl-CoA decarboxylase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); a glutaconyl-CoA decarboxylase and a crotonyl-CoA reductase (alcohol forming); a glutaconyl-CoA decarboxylase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase, or transferase and a crotonate reductase; a glutaryl-CoA dehydrogenase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); a glutaryl-CoA dehydrogenase and a crotonyl-CoA reductase (alcohol forming); a glutaryl-CoA dehydrogenase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase, or transferase and a crotonate reductase; a 3-aminobutyryl-CoA deaminase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); a 3-aminobutyryl-CoA deaminase and a crotonyl-CoA reductase (alcohol forming); a 3-aminobutyryl-CoA deaminase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase or transferase and a crotonate reductase; a 4-hydroxybutyryl-CoA dehydratase, a crotonyl-CoA reductase (aldehyde forming), and a crotonaldehyde reductase (alcohol forming); a 4-hydroxybutyryl-CoA dehydratase and a crotonyl-CoA reductase (alcohol forming); and a 4-hydroxybutyryl-CoA dehydratase, a crotonaldehyde reductase (alcohol forming), a crotonyl-CoA hydrolase, synthetase or transferase and a crotonate reductase. 29-42. (canceled)
 43. The microbial organism of claim 24, wherein said at least one exogenous nucleic acid is a heterologous nucleic acid.
 44. The microbial organism of claim 24, wherein said non-naturally occurring microbial organism is in a substantially anaerobic culture medium. 